Poly(silmethylene)-based polymer blends. II. Synthesis and characterization of poly(diphenylsilmethylene)/poly(methylphenylsilmethylene) blends1

Poly(silmethylene)-Based Polymer Blends. II. Synthesisand Characterization of Poly(diphenylsilmethylene)/Poly(methylphenylsilmethylene) Blends1

TAKUYA OGAWA, MASASHI MURAKAMI

Research Center, Dow Corning Asia Ltd., Yamakita, Kanagawa 258-01, Japan

Received 13 August 1996; accepted 8 November 1996

ABSTRACT: Poly ( diphenylsilmethylene ) ( PDPSM ) / poly ( methylphenylsilmethylene )(PMPSM ) binary polymer blends were synthesized by in situ ring-opening polymeriza-tion of 1,1,3,3-tetraphenyl-1,3-disilacyclobutane in PMPSM . Three catalytic methodsas well as a noncatalytic method were employed. Radical initiators such as an organicperoxide or azo-compound proved to be the effective catalysts in addition to coppercompounds. Blend samples were characterized in detail by DSC, dynamic mechanicalanalysis, solvent extraction, and microscopic observation to clarify the relationshipbetween the preparative method and the properties of these polymer blends. It isstrongly suggested that a part of PMPSM is converted into an insoluble form viaformation of PDPSM–PMPSM block or graft copolymers in the case of the in situcopper-catalyzed polymerization in xylene. The formation of block or graft copolymersis also suggested for samples prepared by the in situ bulk polymerization in the presenceof a radical initiator. However, PMPSMs simultaneously underwent molecular weightdecrease and insolubilization probably due to polymer chain scission and crosslinking,respectively, when the latter method was employed using PMPSM with very high molecu-lar weight. q 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1431–1442, 1997Keywords: poly(silmethylene); in situ polymerization; polymer blend; thermal stability;dynamic mechanical properties; graft copolymers

INTRODUCTION not yet fully identified. Our recent articles havereported the synthesis and basic physical proper-ties9 and thermal and mechanical properties10 ofSilicon-based polymers have been extensively

studied over the past 30 years due to their high the crystalline poly(diarylsilmethylene)s bearingphenyl and tolyl substituents. Poly(methylphe-thermal stability as well as unique optoelectric-

al properties. Poly(silmethylene)s with the re- nylsilmethylene) (PMPSM ) , which is an amor-phous polymer with the glass transition tempera-peating Si{C backbone units are one of the most

well-examined carbosilane polymers, and a num- ture of around 257C, was also demonstrated tober of research activities can be found in the liter- exhibit its excellent 5% weight-loss temperatureature.2–8 Although several reports dealing with as well as good tensile properties.11

the synthesis and the pyrolytic behavior of poly Polymer blend materials are of great interest(silmethylene)s have been published, thermal from both practical and scientific points of view,and mechanical properties of these polymers have but no report has been published regarding poly

(silmethylene)-based polymer blends. We havevery recently reported the synthesis of poly(sil-

Correspondence to: T. Ogawa methylene)-based rigid/flexible binary polymerContract grant sponsor: New Energy and Industrial Tech-blends via in situ polymerization in which a pre-nology Development Organization

q 1997 John Wiley & Sons, Inc. CCC 0887-624X/97/081431-12 cursor compound was polymerized with or with-

1431

96051S/ 8G3E$$051s 03-27-97 12:12:58 polca W: Poly Chem

1432 OGAWA AND MURAKAMI

out catalyst in the presence of flexible silicon-based polymers such as polysiloxanes and polysil-methylenes having methyl groups.1 A new classof phase-separated polymer blends could be ex-pected because each polymer seemed immisciblewith each other for all blend samples. The unique-ness of in situ polymerization methods is simulta-neous preparation of a polymer blend with poly-merization of a precursor material. Many exam-ples have been reported to synthesize blendmaterials utilizing a variety of the in situ polymer-ization techniques including bulk polymeriza-tion,12–15 solution polymerization,16,17 emulsionpolymerization,18 and interfacial polymerization.19

Figure 1. Chemical structures of (a) DDDC , (b)In this article we describe the synthesis andTPDC , (c) PMPSM , (d) PDPSM , (e) DCP , and (f )characterization of poly(diphenylsilmethylene)ACCN .(PDPSM ) /PMPSM binary polymer blends pre-

pared by the in situ polymerization of 1,1,3,3-tet-raphenyl-1,3-disilacyclobutane in PMPSM focus-

1,3-disilacyclobutane (DDDC ) without catalyst.11

ing on morphological differences among blendThe chemical structures of monomers, polymers,samples prepared by various methods. Three cat-and radical initiators in the present study arealytic methods using two types of radical initia-summarized in Figure 1.tors or Cu(acac)2 as well as a noncatalytic bulk

method were examined to provide blend materi-als. Preliminary results have indicated that a part Preparation of Polymer Blendsof flexible polymer seemed to be combined with a

In Situ Bulk Polymerization of TPDCrigid PDPSM when the Cu-aided catalytic methodin PMPSM with DCPwas employed.1 The major purpose of the present

study is to support the hypothesis that a PDPSM- A mixture of 1,1,3,3-tetraphenyl-1,3-disilacyclo-PMPSM block or graft copolymer is formed during butane (TPDC ; 3.5 g; 8.9 mmol), PMPSM (Mw :the in situ copper-catalyzed polymerization. 1.0 1 105; 1.5 g), and DCP (9 mg; 0.033 mmol)

in a glass tube was sealed in vacuo and heated at1407C, which is higher than the melting tempera-

EXPERIMENTAL ture of TPDC (134–1357C), to provide a homoge-neous viscous liquid. This mixture was thenheated at 3007C for 5 h in an oven. After cooling,Materials and Characterization Methodsthe product was crashed then heated in ca. 20 mL

All chemicals including dicumylperoxide (DCP ) of ethanol at the reflux temperature to remove aand 1,1-azobis(cyclohexane-1-carbonitrile) (ACCN) residual monomer. Filtration followed by vacuumare commercially available and were used without drying gave an off-white solid. Yield: 4.69 gfurther purification. Infrared (IR) spectra were (92%). 29Si NMR (CP/MAS, ppm): d Å 011.2,obtained with a Jasco FT/IR-5300 spectrophotom- 014.3, and 016.1.eter. 29Si CP/MAS NMR spectra were recordedwith a Bruker ACP300 spectrometer using 3-tri- In Situ Bulk Polymerization of TPDCmethylsilyl-1-propanesulfonic acid sodium salt as in PMPSM with ACCNan external standard. Gel permeation chromatog-raphy (GPC) was performed using chloroform as A mixture of TPDC (4.0 g; 10.2 mmol), PMPSM

(Mw : 2.3 1 106; 1.0 g), and ACCN (13 mg; 0.05an eluent with a Tosoh HLC-8020 gel permeationchromatograph equipped with two TSKgel mmol) in a glass tube was sealed in vacuo and

heated at 1407C for more than 1 h. The substratesGMHHR-H columns and a refractometer. Polysty-rene standards were used to determine the aver- did not give a completely homogeneous mixture

due to the very high molecular weight of PMPSM .age molecular weights and the polydispersities.PMPSM samples were synthesized by ring-open- The same procedure as descried above was em-

ployed to gave an off-white solid. Yield: 4.56 ging polymerization of 1,3-dimethyl-1,3-diphenyl-


POLY(SILMETHYLENE) POLYMER BLENDS. II 1433

(89%). 29Si NMR (CP/MAS, ppm): d Å 011.1, stant frequency of 1 Hz and a constant strain of0.05%, while the frequency dependence of dy-014.2, and 016.0.namic moduli was examined under a constantstrain of 0.05% at 0, 15, 20, 25, 30, 40, and 507C.

Synthesis of PMPSM with a SiMe3 Terminal Group

DDDC (2.0 g; 7.4 mmol) was heated at aroundMicroscopic Analysis1607C for 90 min under mechanical stirring. After

cooling to ca. 1007C, hexamethyldisiloxane (HMDS, A transmission electron microscope (TEM) analy-8 mL; 37 mmol) was added to the product. Toluene sis was performed using samples sectioned with(20 mL) was added to the mixture, and the re- a microtome at room temperature. A HITACHIsulting clear solution was heated at the reflux tem- H-500 TEM was used at the acceleration voltageperature of HMDS for 1 h. The product was poured of 100 kV to image unstained sections, whereininto 1000 mL of ethanol to form a colorless solid. contrast arises from the electron density differ-The yield after vacuum drying was 1.02 g (50%). ence between phases. Each specimen for the mea-

surement was also prepared by the melt pro-cessing.Thermal Stability of PMPSM Samples

Each PMPSM sample (500 mg) was heated withDCP (5 mg) in the presence or absence of diphe- RESULTS AND DISCUSSIONnylsulfone as a diluent in a sealed tube at 3007Cfor 5.5 h. The molecular weight by GPC of the In Situ Preparation of Polymer BlendsTHF-soluble part and the [THF-insoluble part] /[THF-soluble part] weight ratio were deter- We have previously reported that Cu(acac)2 was

an effective catalyst for in situ polymerization ofmined.TPDC in a silicon-based flexible polymer, and apart of the flexible polymer was converted into

Thermal Analysis an insoluble form by this method, although themechanism of this insolubilization had not beenDifferential scanning calorimetry (DSC) was car-

ried out under a nitrogen atmosphere using a Per- fully understood.1 It seems worthwhile to investi-gate if a radical initiator works in a similar man-kin–Elmer DSC 7/1022 system. The crystalliza-

tion temperatures (Tcs) and the melting tempera- ner as the copper compound to clarify why theflexible polymer became insoluble. Two radicaltures (Tms) of PDPSM in the blend samples were

obtained in the cooling and the second heating initiators, dicumylperoxide (DCP ) and 1,1-azobis-(cyclohexane-1-carbonitrile) (ACCN ) shown inscans, respectively, at a scanning rate of 107C/

min. The glass transition temperatures (Tgs) of Figure 1, were examined in the present study.They were chosen because of their relatively highboth components in the samples prepared by

quenching a molten blends were obtained from decomposition temperatures20 among the com-mercially available solid initiators.the second heating scan at a heating rate of

207C/min. It has already been reported that TPDC poly-merized at 3007C to PDPSM in almost quantita-Thermogravimetry-differential thermal analy-

sis (TG-DTA) was performed using a Rigaku tive conversion.9 First, polymerization of TPDC inthe presence of DCP or ACCN was examined.TG8101D in nitrogen.TPDC was converted to PDPSM in 82% and in95% yields at 200 and 2507C, respectively when

Dynamic Mechanical Analysis 1 mol % of DCP was present. The conversion at2007C is much higher than the value of 5% underDynamic mechanical properties of blend samples

were examined using a Rheometrics RDA II dy- the same reaction conditions for a noncatalyticmethod. ACCN also showed a catalytic activitynamic analyzer in a torsion mode. Melt processing

in the presence of antioxidants (IRGANOX 1010 toward polymerization of TPDC , although theconversion at 2507C was slightly lower than thatfrom Ciba–Geigy Japan Ltd. and phthalocyanine

from Wako Pure Chemical Ind. Ltd.) at 3557C was for DCP-aided polymerization. According to theDSC study, polymers obtained by these methodsapplied to prepare specimens (10 1 35 1 1 mm)

for the measurements. The temperature depen- displayed the melting and crystallization behav-ior being very similar to PDPSM synthesized bydence of dynamic moduli was obtained at a con-



Table I. Synthetic Results of in situ Preparation of PDPSM/PMPSM Blends

Blend Mw (PD)a Methodb [PDPSM ]/[PMPSM ]c Conversion (%)

1 600,000 (2.8) A 87/13 972 F B 58/42 923 F C 67/33 944 F D 67/33 895 100,000 (2.3) A 61/39 956 F B 61/39 427 F C 61/39 928 F D 61/39 869 2,280,000 (2.2) A 73/27 90

10 F B 61/39 1611 F C 73/27 9612 F D 73/27 89

a Molecular weight and polydispersity of PMPSM by GPC.b A: bulk polymerization without catalyst; B: Cu(acac)2-aided polymerization in xylene; C: bulk polymerization with DCP at

3007C; D: bulk polymerization with ACCN at 3007C.c Loaded molar ratio.

noncatalytic bulk polymerization, suggesting that 10 , in which the Cu(acac)2-aided polymerization(Method B) was employed. Several factors includ-these radical initiators are effective as catalysts to

conversion of TPDC to PDPSM . While the active ing the molecular weights of PMPSM and theamount of solvent would affect the conversion,species for the polymerization of TPDC has not

been clarified, an ionic species is believed to be an and diffusion of monomers consequently seems todetermine the coversion of TPDC to PDPSM be-intermediate because of the following three rea-

sons: (a) neither Si{Si nor C{C bonds were cause polymerization of TPDC proceeds heteroge-neously in this method.1formed by the present ring-opening method,21 (b)

Si{C bonds are appreciably polarized, and (c)copper compounds were effective as the catalysts

Characterization of Polymer Blendseven at 1407C. The present positive effect of theradical initiators on the polymerization of TPDC Several analytical methods were applied to differ-implies that the radical intermidiates are proba- entiate blend samples focusing on how the follow-ble at relatively high temperatures. ing two factors affect the morphologies and prop-

In situ bulk polymerization of TPDC in erties of PMPSM , PDPSM , and the PMPSM /PMPSM was carried out next in the presence of PDPSM blends: (a) synthetic methods of the blendsDCP or ACCN to prepare PDPSM /PMPSM (b) the molecular weights (Mws) of PMPSMs.blends. The molecular weights of three PMPSMsamples in the present study ranged from 1.0 Solvent Extraction Study1 105 to 2.3 1 106. The results are summarizedin Table I along with data on Cu(acac)2-aided po- Solvent extraction was examined to see if the solu-

bility of PMPSM was affected in the cases of meth-lymerization in xylene.All samples were heated at 1407C to make them ods C and D. The conversion of PMPSM into an

insoluble form, which is denoted as Xi in the fol-almost homogenous mixtures before heating at3007C. In blends 1–8 homogeneous mixtures were lowing text, is listed in Table II. Xi for each sample

obtained by method A was zero because no chemi-prepared by this process, whereas a part ofPMPSM was not soluble in molten TPDC for cal bonds were present between two components

of the blends.1 On the other hand, insolubilizationblends 9 , 11 , and 12 due to its very high molecularweight. This heterogeneity is critical as will be was observed for polymer blends prepared by

methods C and D as samples by method B showed.discussed later. Conversion of TPDC to PDPSMwas quite high in the cases of catalytic polymer- This suggests some morphological changes of

PMPSMs between samples prepared by methodization using DCP or ACCN (Methods C and D)as well as noncatalytic polymerization (Method A and those by methods C and D, although the

basic polymer structure of PMPSM was main-A). Very low conversion was found in blends 6 and



Table II. Degrees of Insolubilization sized by in situ catalytic methods to prepare sam-of PMPSMs ples that do not contain solvent-soluble PMPSMs.

The results are summarized in Figures 2 and 3,Blend Methoda Xi (%) in which the differences between Tm and Tc of

PDPSM (Tm0Tc ) as a function of Tc and the rela-1 A 0 tionship between PMPSM content and Tc are il-2 B 34

lustrated, respectively.3 C 41It is very interesting that the molecular weight4 D 32

dependence of PMPSM on the preparative5 A 0method–material property relationship was ob-6 B õ 1

7 C 8 served. Blend samples containing PMPSM with8 D 4 the Mw of 105 prepared by method A exhibited9 A 0 lower Tcs and higher Tm–Tc than samples ob-

10 B É 1 tained by method C or method D. The relationship11 C 70 very similar to the above results was obtained12 D 60 when blends in which PMPSM with the Mw of 6

1 105 was incorporated were examined (nota The same codes as those in Table I were used.shown in Figs. 2 or 3). Decreasing Tc as well asincreasing Tm–Tc were also observed when com-pared to the corresponding values of samples ob-tained during the polymerization process ac-tained by the method B. These results can be in-cording to the 29Si NMR analysis of the resulting

blends. The values of Xi for samples obtained bymethod C were greater than those of samples ob-tained by method D regardless of PMPSM . Xis ofsamples by method B were very low in some cases.Although what caused this phenomenon has notbeen identified, heterogeneity of the reaction me-dium resulted from formation of PDPSM1 mustlead to these results. It is also notable that Xi

strongly depends on PMPSM used. Blends 6–8containing PMPSM with the molecular weight of105 exhibited lower Xis than blends 2–4 and 10–12 . This is presumably attributed to the weakinteraction between PDPSM and PMPSM com-pared with those in blends 2–4 and 10–12 . Actu-ally, the microscopic observation of blend samplesshowed appreciable differences among samples,which will be discussed later.

DSC Study

The transition temperatures of polymer blendsare of great interest to gain insights into the mor-phological difference among these materials. Thepreliminary results showed, however, PDPSM /PMPSM blends had two glass transition tempera-tures (Tgs), each of which was the same as thatof the component polymer, and no significant dif-ference was observed among the samples synthe- Figure 2. Tm 0 Tc as a function of Tc for PDPSM /sized by the different methods.1 DSC measure- PMPSM blends. Mw of PMPSM : (A) 1 1 105, (B) 2.3ments of various blend samples were made in the 1 106. square: blends prepared by method A, circle:present study to see how PMPSM affects the melt- blends prepared by method C, triangle: blends prepareding and crystallization behavior of PDPSM . Sol- by method D, cross in square: PDPSM prepared by

method A.vent extraction was performed for blends synthe-



Dynamic Mechanical Analysis

The present study focused on the measurementsof dynamic mechanical properties of PDPSM /PMPSM blends to identify the differences amongthe samples prepared by the various methods.The measurements were made in a torsion modeusing melt-processed specimens. Figure 4(A) and(B) display the temperature dependence of stor-age modulus (G * ) and tangent delta (tan d ) , re-spectively, of two blends with different PMPSMcontents prepared by the method A along with theprofiles of PDPSM and PMPSM . These two blendsexhibited two major transitions at 30 and 1407Cin Figure 4(B), both of which did not shift byaltering the PMPSM content. The extent of thedrop in G * at each transition temperature is pro-portional to the amount of each component poly-mer. Furthermore, the transition temperatureswere identical to those of the corresponding com-ponent polymers. It is, therefore, evident thatPDPSM and PMPSM are immiscible with eachother.

Figure 5(A), (B), and (C) also show the tem-perature dependence of tan d for the blends pre-pared using PMPSMs with different Mws. EachFigure 3. Relationship between the PMPSM contentfigure depicts dynamic mechanical data of blendsand Tc for PDPSM /PMPSM blends. Mw of PMPSM : (A)prepared by catalytic and noncatalytic methods1 1 105, (B) 2.3 1 106. The same legends as those inwith almost the same PDPSM /PMPSM molar ra-Figure 2 were used.tios. According to Figure 5(A) and (B), the mobil-ity of PMPSMs in the catalytically preparedblends seems to be restrained, as suggested byterpreted as highly retarded crystallization ofthe smaller peaks at around 307C. On the otherPDPSM in the samples prepared by the method Ahand, blends in which PMPSM with the highestcompared to the samples prepared by the catalyticMw of 2.3 1 106 was incorporated gave good simi-methods probably due to the weaker interactionlarity in the mobility of PMPSMs. The differencebetween PDPSM and PMPSM .22 It also should bein the mobility of PMPSM is more clearly demon-noted that the greater the PMPSM content, thestrated by employing the frequency-sweep test.lower the Tc , as depicted in Figure 3(A). ThisFrequency spectra of dynamic modulus were mea-indicates the crystallization retarding effect ofsured at various temperatures near the Tg ofPMPSM . Taking these DSC and solvent extrac-PMPSM , and each spectrum was combined by us-tion results into account, there should be an ap-ing a time–temperature superposition techniquepreciable difference in morphologies of the blendsto provide a master curve. The tan d master curvescaused by the chemical interaction probably viaof blends containing PMPSM with the Mw of 1.0polymer terminals between the samples prepared1 105 prepared by the catalytic and noncatalyticby the catalytic and noncatalytic methods. On themethods are illustrated in Figure 6. It is obviousother hand, a significant difference among thethat PMPSM in the catalytically prepared samplesamples was not observed when the Mw ofshows the smaller peak than that in the blendPMPSM was 2.3 1 106, suggesting that the de-obtained by the noncatalytic method, suggestinggree of retarding of PDPSM crystallization bythat the former can move more restrictedly thanPMPSM does not depend on the preparativethe latter. On the other hand, a very good similar-method but on the PMPSM content. Because theity of the master curves was found between sam-Mw of the PMPSM was very high, the interactionples containing PMPSM with the Mw of 2.3 1 106of the polymer end groups of PDPSM and PMPSM

would not be critical for PDPSM crystallization. (not shown in the text). It is, therefore, concluded



method and affects the transitions of both PDPSMand PMPSM .

The experimental results obtained in solventextraction, DSC study, and dynamic mechanicalanalysis can be explained by the hypothesis that

Figure 4. Temperature dependence of (A) storagemodulus (G * ) and (B) tangent delta (tan d ) of PDPSM /PMPSM blends with different PMPSM contents. (a)PDPSM , (b) PDPSM /PMPSM (molar ratio: 87/13), (c)PDPSM /PMPSM (molar ratio: 61/39), (d) PMPSM .

that the mobility of PMPSMs in the blends pre-pared by the catalytic methods is restrained tosome extent when PMPSM samples with lowerMw were incorporated, whereas PMPSMs withthe highest Mw tend to behave in a similar mannerregardless of the preparative methods.

It is also notable that a relatively weak transi-Figure 5. Temperature dependence of tan d fortion found at around 2007C in Figure 5(B) andPDPSM /PMPSM blends. (A) PDPSM /PMPSM Å 87/(C), which can be assigned to the crystalline tran-13 (molar ratio) , Mw of PMPSM : 6.0 1 105; blendssition of PDPSM , 10 was affected by preparativeprepared by (a) method A and (b) method B. (B)

methods of the blends. The transitions of the cata- PDPSM /PMPSM Å 60/40 (molar ratio) , Mw oflytically prepared blends were weaker than those PMPSM : 1.0 1 105; blends prepared by (a) method Aprepared by the noncatalytic method. These phe- and (b) method C. (C) PDPSM /PMPSM Å 72/28 (mo-nomena suggest that the interaction between lar ratio) , Mw of PMPSM : 2.3 1 106; blends prepared

by (a) method A and (b) method C.PDPSM and PMPSM is altered by the preparative



Figure 6. The tan d master curves of blends prepared by (a) method A and (b) methodB. Mw of PMPSM : 1.0 1 105.

the formation of PDPSM-PMPSM block or graft of PDPSM-PMPSM copolymers, and is consistentwith the SEM analytical results.1 The differencecopolymers took place in the cases of catalytic po-

lymerization methods (methods B, C, and D). between blends 5 and 7 , however, was not ob-served. This phenomenon is probably explainedThese copolymers may interact with both PDPSM

and PMPSM playing the role of compatibilizer. by an insufficient amount of the PDPSM-PMPSMcopolymers for blend 7 . In fact, this sample exhib-ited very low Xi compared with samples 2 and 11 .Microscopic Observation

The effect of molecular weights of PMPSM toA morphological study by means of a transmission the morphologies can be observed in Figure 7(A),electron microscope (TEM) aids in understanding (C), and (E). The size of the dispersed PDPSMthe process–structure–property relationship of obviously decreases with increasing molecularthis polymer blend system. TEM micrographs of weights of PMPSM . Hence, the dispersion size ofblend 1 , a THF-insoluble part of blend 2 , blends PDPSM seems to be affected by both the molecu-5 , 7 , 9 , and 11 are shown in Figure 7(A) – (F), lar weights and the Xi of PMPSM used.respectively. The THF-insoluble part of blend 2had almost the same [PDPSM ] / [PMPSM ] molar Thermostability of PMPSMsratio as blend 1 did. In each micrograph, a darkpart and a light part can assigned to PDPSM and Various analytical and morphological evidence in

the present study appears to indicate the in situPMPSM , respectively. One can easily distinguishan evident difference in the morphology by refer- formation of PDPSM-PMPSM block or graft copol-

ymers in the blends prepared by the catalyticring to Figure 7(A), (B), (E), and (F). The cata-lytically prepared samples [Fig. 7(B) and (F)] methods. The thermostability of this polymer was

examined by employing heating conditions verydisplayed more finely-dispersed texture than thenoncatalytically prepared samples [Fig. 7(A) and similar to the in situ preparation of PDPSM /

PMPSM blends because degradation of PMPSM(E)] . This suggests an improvement of compati-bility between PDPSM and PMPSM in the cata- to an insoluble material upon heating at 3007C23

can be a possible reason to explain the above ex-lytically prepared samples due to the formation



Figure 7. TEM micrographs of (A) blend 1, (B) a THF-insoluble part of blend 2 , (C)blend 5 , (D) blend 7 , (E) blend 9 , and (F) blend 11 .

perimental results. Three PMPSM samples were form without any soluble fractions while main-taining its appearance by heating without DPS ,heated with DCP in a sealed tube, and each prod-

uct was characterized by GPC. The solubility and whereas it remained unchanged in solubilitywhen it was heated in DPS , although the Mw de-the molecular weights (Mw ) of the products are

summarized in Table III. creased appreciably. Because these two PMPSMswere soluble in DPS to form a homogeneous solu-Each sample was heated with or without diphe-

nylsulfone (DPS : PhSO2Ph) as a diluent to exam- tion, the above results suggest that the homogene-ity of the reaction medium is essential to the insol-ine if homogeneity of a reaction medium is critical

to conversion of PMPSM into an insoluble form. ubilization of PMPSM . Heating without the sol-vent, which seems to have an equivalent effect toDPS was chosen because of its low volatility and

high thermal stability in addition to the slight the thermal treatment in bulk, makes this poly-mer solvent-insoluble, probably due to crosslink-structural similarity with TPDC . P-2 exhibited

almost no change in the Mw as well as its appear- ing. The results for P-3 support this hypothesis.Because this sample did not make a homogeneousance. P-1 was converted into a THF-insoluble



Table III. Thermal Stability of Three PMPSM Samples

Mwa Solubilityb (Mw

c) Solubilityb (Mwc)

Polymer ID Before Heating Heating w/o Solvent Heating in Ph2SO2

P-1 6.0 1 105 Insoluble Soluble (1.0 1 105)P-2 1.0 1 105 Soluble (1.2 1 105) Soluble (1.2 1 105)P-3 2.3 1 106 Insoluble Insoluble (2.2 1 105)

a Weight-average molecular weight relative to polystyrene standards.b Tested in THF.c Mws of THF-soluble components were in parentheses.

mixture with DPS due to its high Mw , a part of the method B was caused by the in situ formationthis sample seemed to be heated in bulk even in of PDPSM-PMPSM block copolymers.the presence of DPS . Hence, the product becamepartially soluble with approximately 20% of THF-insoluble components. The Mw of the THF-soluble In Situ Polymerization of TPDC with Compoundscomponents decreased, as was observed for P-1 . Bearing an Si{OH GroupThe main chain scission is taking place underthese heating conditions because the decrease of We employed several analytical tools describedthe Mw was also found when these samples were above to provide evidences for the in situ forma-heated at 3007C without DCP , and no change was tion of block or graft copolymers during polymerdetected from the NMR analysis of the solvent- blend synthesis. One possible explanation for thesoluble products. In fact, the Mw of P-3 decreased copolymer formation is initiation of TPDC poly-from 2.3 1 106 to 8.7 1 105 by heating without merization at a terminal Si{OH group ofDCP . Taking these results into account, P-3 un- PMPSM . The Xi should diminish when PMPSMdergos polymer chain scission and crosslinking, with lower Si{OH content is used if this hypoth-which takes place simultaneously upon heating.24

esis is correct. Ring-opening polymerization ofThe degree of the molecular weight decrease as DDDC followed by termination using hexameth-well as the Xi of the product may depend on the yldisiloxane was examined expecting to yieldhomogeneity of the samples upon heating. It has PMPSM in which a part of terminal groups werealready been descried in the Solvent Extraction converted to Si{O{SiMe3 groups. According tosection that about 70% of PMPSM was converted the IR analysis, the [Si{OH]/[SiMe] intensityinto the insoluble form when in situ polymeriza-

ratio of this sample was 0.021 { 0.02 while thattion of TPDC in PMPSM was performed in theof PMPSM in blend 1 was 0.029{ 0.02 suggestingpresence of DCP . Because this conversion valuethat PMPSM with lower Si{OH content wasis much higher than the present data of 20%, ayielded. The Xi value for the in situ polymeriza-part of the insolubilized PMPSM is suggested totion using this sample was 19%, which wasbe PDPSM–PMPSM block or graft copolymerssmaller than that in blend 1 .formed during the in situ polymerization. The

An experiment using a smaller Si{OH com-block copolymers can be formed by the main chainpound seems to give more direct evidence. Thescission while the graft copolymer formation canCu(acac)2-aided polymerization of TPDC was per-be achieved by initiation of TPDC polymerizationformed in the presence of 5 mol % of hydroxytri-on side groups of PMPSM , which is similar to aphenylsilane. The reason why this was used as acrosslinking mechanism. Several types of reac-model compound is the high stability of the silanoltions described in this section are presumably pos-group. Despite its sterical bulkiness, the polymer-sible for the ACCN-aided in situ polymerization.ization product displayed a weak resonance atNeither main chain scission nor crosslinking026.5 ppm in the 29Si NMR spectrum, which canof PMPSM occurs from heating at relatively lowbe assigned to the terminal silicon (Ph3SiOSi) oftemperature of 1407C, at which the in situ poly-PDPSM. This result supports the hypothesis thatmerization of TPDC in the presence of Cu(acac)2

a silanol group can be a reactive site for polymer-was carried out. This supports the hypothesis thatthe insolubilization found for blends prepared by ization of TPDC .



lished: N. S. Nametkin and V. M. Vdovin, Izv.CONCLUSIONSAkad. Nauk SSSR, Ser. Khim., 1153 (1974).

5. G. Levin and J. B. Carmichael, J. Polym. Sci., PartThe present study gave several pieces of informa-A-1, 6, 1 (1968).tion about the structure–property relationship of

6. (a) H.-J. Wu and L. V. Interrante, Chem. Mater.,PDPSM /PMPSM binary blend system. Polymer 1, 564 (1989); (b) H.-J. Wu and L. V. Interrante,blend samples were prepared by in situ polymer- Macromolecules, 25, 1840 (1992); (c) L. V. In-ization of TPDC to PDPSM in PMPSM . Although terrante, H.-J. Wu, T. Apple, Q. Shen, B. Ziemann,both components in these blends synthesized by D. M. Narsavage, and K. Smith, J. Am. Chem. Soc.,in situ polymerization methods were immiscible 116, 12085 (1994); (d) I. L. Rushkin and L. V. In-with each other, the morphology of the blends can terrante, Macromolecules, 28, 5160 (1995); (e) I. L.

Rushkin and L. V. Interrante, Macromolecules, 29,be modified by altering the synthetic methods and3123 (1996).PMPSM incorporated. It was demonstrated by

7. R. M. Laine and F. Babonneau, Chem. Mater., 5,various analytical data that a part of PMPSM ,260 (1993).which has good solubility in common solvents,

8. (a) F. Koopmann and H. Frey, Macromol. Rapidwas converted into an insoluble form probably viaCommun., 16, 363 (1995); (b) F. Koopmann andthe formation of PDPSM–PMPSM block or graftH. Frey, Macromolecules, 29, 3701 (1996).(probably block) copolymers when the in situ Cu-

9. T. Ogawa, M. Tachikawa, N. Kushibiki, and M.(acac)2-aided polymerization was employed. The Murakami, J. Polym. Sci., Part A, Polym. Chem.,products of the in situ polymerization reactions 33, 2821 (1995).with a radical initiator were strongly affected by 10. T. Ogawa and M. Murakami, J. Polym. Sci., Partthe homogeneity of the reaction medium. The mo- B: Polym. Phys., 34, 1317 (1996).lecular weight decrease of PMPSM caused by 11. T. Ogawa and M. Murakami, Chem. Mater., 8, 1260main chain scission and insolubilization, which is (1996).attributable to crosslinking, were observed when 12. Y. Chen, R. Qian, G. Li, and Y. Li, Polym. Com-

mun., 32, 189 (1991).the reaction proceeded heterogeneously. How-13. R. A. Gaudiana, T. Adams, and R. S. Stein, Macro-ever, the crosslinking did not take place because

molecules, 25, 1842 (1992).a chain scission reaction would preferentially pro-14. (a) M. Trznadel, P. Milczarek, and M. Kryszewski,ceed when homogeneity of the reaction mixture

J. Appl. Polym. Sci., 43, 1125 (1991); (b) M. Trzna-was maintained.del, M. Pluta, and M. Kryszewski, ibid, 49, 1405(1993); (c) M. Trznadel, M. Pluta, and M. Kryszew-

Total support throughout this work performed under ski, ibid, 50, 637 (1993).the management of the Japan High Polymer Center as 15. (a) P. Muller, C. Worner, and R. Mulhaupt, Mac-an Industrial Science and Technology Frontier Pro- romol. Chem. Phys., 196, 1929 (1995); (b) C.gram by the New Energy and Industrial Technology Worner, P. Muller, and R. Mulhaupt, Polym. Bull.,Development Organization is gratefully acknowledged. 34, 301 (1995).The authors are also grateful to Dr. Brian M. Naasz

16. (a) N. Ogata, K. Sanui, and H. Itaya, Polym. J.,and members in his group of Dow Corning Corp. for22, 85 (1990); (b) K. Sanui, N. Ogata, K. Kamitani,generous gifts of disilacyclobutanes.and M. Watanabe, J. Polym. Sci., Part A: Polym.Chem., 31, 597 (1993); (c) N. Ogata, Macromol.Symp., 84, 267 (1994); (d) Y. Ayaki, M. Rikukawa,

REFERENCES AND NOTES M. Watanabe, K. Sanui, and N. Ogata, Polym. J.,26, 325 (1994); (e) K. Sanui, Y. Kiyohara, M. Riku-kawa, and N. Ogata, Reactive Funct. Polym., 30,1. Part I of this work: T. Ogawa and M. Murakami,293 (1996).J. Polym. Sci., Part A Polym. Chem., 35, 399 (1997).

17. H. S. Yoon, K. U. Kim, J. Lee, Y. Lee, S. S. Hwang,2. D. R. Weyenberg and L. E. Nelson, J. Org. Chem.,T. S. Park, J. Cho, J. Kim, B. I. Ahn, K. Char, and30, 2618 (1965).R. P. Quirk, Macromol. Symp., 95, 303 (1995).3. W. A. Kriner, J. Polym. Sci., Part A-1, 4, 444

18. D. J. Hourston and J. Romaine, J. Appl. Polym.(1966).Sci., 43, 2207 (1991).4. (a) N. S. Nametkin, V. M. Vdovin, and V. I. Zav’ya-

19. E. Debeaupte, M. Watanabe, K. Sanui, and N.lov, Dokl. Akad. Nauk SSSR, 162, 824 (1965); (b)Ogata, Chem. Mater., 4, 1123 (1992).N. S. Nametkin, V. M. Vdovin, and A. V. Zelenaya,

20. The ten-hours half-life decomposition temperatureDokl. Akad. Nauk SSSR, 170, 1088 (1965); (c)of DCP and ACCN are 117 and 887C, respectively.N. S. Nametkin and co-workers have thoroughly

21. The Wurtz coupling reaction of diphenyldichlorosi-investigated the synthesis and reactions of poly(sil-alkylene)s. A review article on this has been pub- lane and dibromomethane in the presence of so-



dium provided polycarbosilanes bearing Ph2SiCH2, zero when this polymer was heated at the rate of107C. It also has been reported in ref. 11 that thisCH2CH2, and Ph2SiSiPh2 units: B. van Aefferden,

W. Habel, and P. Sartori, Chemiker-Ztg., 114, 367 polymer underwent decomposition via evolution ofbenzene, not via backbiting to form cyclic species.(1990).

22. The crystallization rate of a crystalline polymer is 24. Rates of crosslinking and chain scission duringthermal degradation at 3807C have been studiedlowered by blending of an immiscible amorphous

polymer: T. T. Wang and T. Nishi, Macromolecules, by using soluble aromatic polymers: S. Kuroda, K.Terauchi, K. Nogami, and I. Mita, Eur. Polym. J.,10, 421 (1977).

23. The weight loss of PMPSM below 3507C is almost 25, 1 (1989).


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