Supporting Information for \"Direct Thiol-Ene Photocoating of Polyorganosiloxane Microparticles

$Page 1: Supporting Information for \"Direct Thiol-Ene Photocoating of Polyorganosiloxane Microparticles$
S1

Supporting Information for Publication

Direct Thiol-Ene Photocoating of Polyorganosiloxane

Microparticles

Christian Kuttner,* ,a Petra C. Maier, a Carmen Kunert, a

Helmut Schlaad, b and Andreas Fery *,a

a Department of Physical Chemistry II, University of Bayreuth, Bayreuth 95440, Germany

d Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam 14424, Germany

* E-mail: [email protected], [email protected]

1. Applied UV Irradiation

Figure S1. Emission spectrum of the applied UV lamp (overlayed in red color) as a result of a

Hg lamp and a blue filter (transmission, dashed line).

S2

2. Dye Adsorption onto Polyorganosiloxane Particles

Figure S2. Dye p-(dimethylamino) azobenzene (dimethyl yellow): (a) pH-dependent color

change; (b) image of exemplary samples drawn from the reference solution without particles

(left, yellow) and from the particles solution (right, red); (c) image of exemplary samples after

centrifugation before UV/Vis analysis (sedimented particles are red, supernatant is yellow).

S3

3. Photoinitiation by UV Light – Thiyl Formation

In 1928, Ashworth and Burkhardt found that light accelerates the addition of thiols to olefins,

particularly ultraviolet light. [1] Therefore, thiyls can be formed by homolysis of the SH bond

upon UV-irradiation. However, olefins and alkylmercaptans absorb UVC light but virtually no

light above 280 nm. Therefore, UVC light is capable to from thiyls, whereas UVA light is

not. [2,3]

By 1991, Klemm and Sensfuß published several studies[4-6] on photopolymerization,

photoinitiation at 365 nm, and on the influence of oxygen. One major result was that oxygen has

no significance influence on thiyl formation. [6]

The other major finding was that radicals were only detected in the presence of an olefin, which

lead to the proposition that a thiol-olefin charge-transfer (CT) complex is responsible for

photoinitiation. [6] Such a CT complex has been proposed before in context of thiol-ene

cooxidation by Szmant and co-workers. [7,8] The two structural proposals are a π-olefinic

complex and a hydrogen-bonded complex. [7,9] By UVA-irradiation, the CT complex absorbs

light and dissociates upon thiyl formation.

In 2002, Cramer et al. reported that the radical generation rate differs dramatically for UVA

(315 nm < λ < 380 nm) and UVC light (200 nm < λ < 280 nm). Although, thiol-ene photo-

polymerizations proceeded with light centered around 365 nm, the reaction was significantly

faster when 254 nm light was used. [10] It has been found that the initiation rate for UVA light is

proportional to the concentration of ene-functional groups — whereas for UVC light this is not

the case. The latter is proportional to the concentration of thiols. [11]

The corrected mechanism reads as

(S1)

(S2)

Photolytic initiation by UVC light is a first-order reaction and proceeds at much higher rates than

the UVA-mediated second-order process. [10] If olefins are available in excess, UVA-initation is

pseudo first-order. Figure S3 shows a schematic mechanism of thiyl formation by UV light.

R’—SHh⌫,254 nm�! R’—S⇤ +H⇤

R’—SH + H2C=CHR ��! � [CT-complex]h⌫,365 nm�! R’—S⇤ +H3C—C⇤HR

S4

Figure S3. Schematic mechanism of thiyl formation by UV photoinitiation.

For 365 nm light, not one but two unsaturated species are required to form a growing chain. The

active olefin species (formed in the initial initiation process) may also contribute to the formation

of thiyls by sufhydryl H-abstraction. However, the likelihood of this event strongly depends on

the concentration ratio of olefins to thiols, further reactants, and the solvent. In any case, the

majority of thiyls are formed by direct photoinitiation and only a small fraction can be attributed

to subsequent radical transfer reactions. In all synthetic approaches of this work, UVA light with

a maximum intensity at 365 nm has been used (see Figure S1), consequently without additional

photoinitiator.

S5

4. Scanning Electron Micrographs of Polystyrene-Coated Polyorganosiloxane Particles

Figure S4. Scanning electron mircographs of polystryrene-coated polyorganosiloxane

microparticles after different times of polymerization.

S6

5. Dynamic Light Scattering of Photocoated and Uncoated Particles

Figure S5. Size-dispersity (PDI) determined by dynamic light scattering of uncoated

polyorganosiloxane particles in toluene (a) and ethanol (b).

a b

c d

a b

c d

a b20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

Uncoated particlesin toluenePDI = 0.047

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

Uncoated particles in ethanolPDI = 0.048

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB854-b-PS360PDI = 0.089

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB43-b-PS360PDI = 0.094

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB339-b-PS360PDI = 0.064

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB663-b-PS360PDI = 0.089

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

HSP@PS 6hPDI = 0.041

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


S7

Figure S6. Dynamic light scattering of diblock copolymer-coated particles in toluene:

(a) PB43-b-PS360, (b) PB339-b-PS360, (c) PB663-b-PS360, and (d) PB854-b-PS360.

a b

c d

a b

c d

1000

800

600

400

200

0

Γ , H

z

1.0x10-30.80.60.40.20.0q2, nm-2

PB43-b-PS360 in tol. λ = 632.8 nmRh = (583 ± 6) nmPDI = 0.094

1000

800

600

400

200

0

Γ, H

z

1.0x10-30.80.60.40.20.0q2, nm-2


1000

800

600

400

200

0

Γ , H

z

1.0x10-30.80.60.40.20.0q2, nm-2

PB663-b-PS360 in tol. λ = 632.8 nmRh = (617±5)nmPDI = 0.089

1000

800

600

400

200

0

Γ, H

z

1.0x10-30.80.60.40.20.0q2, nm-2


1000

800

600

400

200

0

Γ , H

z

1.0x10-30.80.60.40.20.0q2, nm-2

HSP@PS 12h λ = 532 nmRh = (642 ± 4) nmPDI = 0.11

1000

800

600

400

200

0

Γ , H

z

1.0x10-30.80.60.40.20.0q2, nm-2


1000

800

600

400

200

0

Γ, H

z

1.0x10-30.80.60.40.20.0q2, nm-2


1000

800

600

400

200

0

Γ, H

z

1.0x10-30.80.60.40.20.0q2, nm-2


S8

Figure S7. Size-dispersity (PDI) determined by dynamic light scattering of diblock copolymer-

coated particles in toluene: (a) PB43-b-PS360, (b) PB339-b-PS360, (c) PB663-b-PS360, and (d) PB854-b-

PS360.

a b

c d

a b

c d

a b20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB854-b-PS360PDI = 0.089

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB43-b-PS360PDI = 0.094

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB339-b-PS360PDI = 0.064

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB663-b-PS360PDI = 0.089

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


S9

Figure S8. Dynamic light scattering of polystyrene-coated particles in toluene: (a) 6 h, (b) 12 h,

(c) 18 h, and (d) 24 h.

a b

c d

a b

c d

1000

800

600

400

200

0

Γ , H

z

1.0x10-30.80.60.40.20.0q2, nm-2


1000

800

600

400

200

0

Γ, H

z

1.0x10-30.80.60.40.20.0q2, nm-2


1000

800

600

400

200

0

Γ , H

z

1.0x10-30.80.60.40.20.0q2, nm-2

PB663-b-PS360 in tol. λ = 632.8 nmRh = (617±5)nmPDI = 0.089

1000

800

600

400

200

0

Γ, H

z

1.0x10-30.80.60.40.20.0q2, nm-2


1000

800

600

400

200

0

Γ , H

z

1.0x10-30.80.60.40.20.0q2, nm-2


1000

800

600

400

200

0

Γ , H

z

1.0x10-30.80.60.40.20.0q2, nm-2


1000

800

600

400

200

0

Γ, H

z

1.0x10-30.80.60.40.20.0q2, nm-2


1000

800

600

400

200

0

Γ, H

z

1.0x10-30.80.60.40.20.0q2, nm-2


S10

Figure S9. Size-dispersity (PDI) determined by dynamic light scattering of polystyrene-coated

particles in toluene: (a) 6 h, (b) 12 h, (c) 18 h, and (d) 24 h.

a b

c d

a b

c d

a b20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB854-b-PS360PDI = 0.089

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB43-b-PS360PDI = 0.094

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB339-b-PS360PDI = 0.064

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI

PB663-b-PS360PDI = 0.089

20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


20

15

10

5

0

Nor

m. P

roba

bilit

y, %

0.50.40.30.20.10.0PDI


S11

6. Calculation of the Coating Thickness of Spherical Core/Shell Particles from TGA Mass Loss

The volume of the uncoated particle Vcore is given by its radius r, and the volume of the coating

Vshell is a shell of thickness t. The mass fraction of polymer shell wshell and core particle wcore are

given by the mass loss.

(S3)

(S4)

(S5)

where ρ is the bulk density. Rearrangement of Eqn. S6 yields

(S6)

Eqn. S6 can be solved for t. The coating thickness of spherical particles can be calculated from

the TGA mass loss with the following Equation.

(S7)

Using wcore = 1-wshell, the uncertainty of the thickness value can be calculated using Gaussian

error propagation and the respective derivations.

(S8)

(S9)

(S10)

(S11)

0 =

✓t

r

◆3

+ 3

✓t

r

◆2

+ 3

✓t

r

◆� w

shell

wcore

%core

%shell

t =

✓3

r1 +

wshell

wcore

%core

%shell

� 1

◆r =

✓3

r1 +

wshell

1� wshell

%core

%shell

� 1

◆r

@r t =

✓3

r1 +

wshell

1� wshell

%core

%shell

� 1

◆=

t

r

@%shell

t =1

3r

wshell

wshell

� 1

%core

%2shell

✓%core

%shell

wshell

1� wshell

+ 1

◆�2/3

@%core

t =1

3r

wshell

1� wshell

%�1

shell

✓%core

%shell

wshell

1� wshell

+ 1

◆�2/3

@wshell

t =1

3r%core

%core

(wshell

� 1)�2

✓� %

core

%shell

wshell

wshell

� 1+ 1

◆�2/3

wshell

wcore

=m

shell

mcore

=%shell

Vshell

%core

Vcore

with Vi =4

3⇡ r3i

=%shell

%core

V(r + t)� V(r)V(r)

=%shell

%core

"✓t

r+ 1

◆3

� 1

#

S12

Combination allows for calculation of the thickness variance σt2 based on the measurement

uncertainty σw,shell, the model uncertainty σρ, and the size dispersity of the core particles σr.

(S12)

(S13)

Assumed errors are 0.1 g/cm3 for the densities, 70 nm for the radius (DLS, σRh/ ), and 0.5% for

the mass loss.

7. Simplified Estimation for Polymer-Coated Polyorganosiloxane Particles

Upon assumption of a linear correlation of the relative coating thickness t/r and the polymer

content (mass loss) wshell, a simplified estimation for polymer-coated polyorganosiloxane

particles with r = 485 nm (Rh in ethanol) can be formulated:

(S14)

where, kρ represents the density ratio of core to shell. Error by Gaussian error propagation:

(S15)

with assumed errors of σr = 70 nm (DLS, σRh/ ) and σw,shell = 0.5%.

p2

p2

�2

t =(@r t)2 �2

r + (@wshell

t)2 �2

wshell

+ (@⇢shell

t)2 �2

⇢shell

+ (@⇢core

t)2 �2

⇢core

⇡fsize dispersity

(r, t) + fTGA

(wshell

) + fmodel

(�%)

�t ⇡ 0.741q

w2shell �

2r + r2 �2

wshell

t ⇡ 0.741 r wshell for polymer on polyorganosiloxane k% =2

1

S13

8. Thermogravimetric Analysis of Polymer-Coated Particles

Figure S10. Scaling behavior of the relative coating thickness to the polymer content (TGA

mass loss). The dashed lines are based on Eqn. S7. The bulk density ratio kρ is an important

scaling factor in this calculation, defining the core/shell system (polymer on polymer particle

kρ ≈ 1, polymer on polyorganosiloxane particle kρ ≈ 2, polymer on pure silica particle kρ ≈ 2.5).

The linear fit is based on Eqn. S15 (red line).

130314 P8 5er Serie.pxp

130314 TGA 5Vol% + Referenzsilica

density between 1 and 2.5

1 PDMS 2.5 silica1.5 siloxanes

a

b

0.741

t /r = 0.23

1.5

1.0

0.5

0.0

Rel

ativ

e co

atin

g th

ickn

ess t /r

100806040200Polymer content (mass loss), %

kρ = 2.5, 2.0, 1.5, 1.0

100

90

80

70

60

50

40

30

Mas

s lo

ss (T

GA)

, %

8006004002000Temperature, °C

pure silica

hybrid silica

12h

3h

6h

18h 24h

30

25

20

15

10

5

0

Poly

mer

con

tent

(mas

s lo

ss),

%

0 3 6 12 18 24Polymerization time, h

100

80

60

40

20

0

Coating thickness, nm

uncoatedpolyorgano-

siloxane 1.0

0.5

0.0

Rel

ativ

e co

atin

g th

ickn

ess t /r

7550250Polymer content (mass loss), %

kρ = 2.5, 2.0, 1.5, 1.0

t /r = 0.23

S14

9. Raman Spectroscopy of Polystyrene-Coated Particles

Figure S11. Raman spectra of polystyrene-coated particles with different polymerization times.

(a) Overview of the complete spectra, normalized for the area under the vibrations of aliphatic

CH2 at 2800 to 3000 cm-1. (b) Detail spectra of the range of 400 to 1750 cm-1 with vibrational

assignments. From the changes of the Raman signals, the increase of the coating thickness for

longer polymerization times can be followed. Figure S12 presents the normalization procedure.

Table S1 gives an overview of the observed Raman frequencies and vibrational assignments.

a

b 1500

1000

500

0

Norm

alize

d in

tens

ity, a

.u.

1600140012001000800600400Raman shift, cm-1

νSiC

νCC

δCH2

ωCH2

νCCar.

δOSiO

νphenylνSiOSi

νCC

αCCC, phenyl

γCH, ar.

νCC, phenyl

TCH2

0h 3h 6h12h18h24h

5000

4000

3000

2000

1000

0

Nor

mal

ized

inte

nsity

, a.u

.

40003600320028002400200016001200800400Raman shift, cm-1

0h 3h 6h12h18h24h

S15

Figure S12. Procedure used to normalize the spectra for the area under the vibrations of aliphatic

CH2 at 2800 to 3000 cm-1: The respective frequency range of each Raman spectrum was

processed by a multi-peak fitting using IGOR Pro by WaveMetrics. The measured spectra could

be described by 6 to 8 Voigt signals. The residuals, indicated above each fit in red color, were

below 5%. A normalization factor was calculated based on the areas of the individual Voigt fits.

(a) 0h, uncoated particles; (b) 3h; (c) 6h; (d) 12h; (e) 18h; and (f) 24h of polymerization time.

12001000

800600400200

0

40003500300025002000

Raman shift, cm-1

1200

800

400

0

-400

40

Location: 2566.2Area: 33544Location: 2668.5Area: 250.48

Location: 2799.9Area: 924.67 Location: 2860.8

Area: 9117.4

Location: 2888.8Area: 36743


Location: 2963.5Area: 9186.5

P8 uncoated 800

600

400

200

0

40003500300025002000

Raman shift, cm-1

800600400200

0

-40-20

02040




Location: 2916.5Area: 35546 Location: 2961.9

Area: 13135




P8S3

400

300

200

100

0

40003500300025002000

Raman shift, cm-1

400300200100

0

-20-10

01020








P8S6 800

600

400

200

0

40003500300025002000

Raman shift, cm-1

800600400200

0

-40-20

02040






Location: 3038Area: 4078.9



P8S12

800

600

400

200

0

40003500300025002000

Raman shift, cm-1

800600400200

0

-40-20

02040








P8S24

800600400200

040003500300025002000

Raman shift, cm-1

800

600

400

200

0

-40-20

02040







P8S18

a b

c d

e f

0h

6h

18h 24h

12h

3h

residuals

residuals

residuals residuals

residuals

residuals

data+fit

data+fit

data+fit data+fit

data+fit

data+fit

fit

fit fit

fit

S16

Table S1. Observed vibrational frequencies of uncoated polyorganosiloxane particles (left),

prepared from MPTMS as precursor, and additional vibrational frequencies after photocoating

with polystyrene (right) via “grafting-from”. Vibrational assignments are based on [12] and [13].

Polyorganosiloxane Particles Polystyrene-Coated Particles

Raman shift, cm-1 Assignment Raman shift, cm-1 Assignment 511 ν(SiOSi) or δ(OSiO)

620 ν(CC) 651, 696 ν(SiC)

742 ν(SC) 759 α(CCC) phenyl

ring deformation 807 δ(CSH)

827 γ(CH) aromatic 863, 919 γ(CH2)

1003 ν(CC) 1001 ν(CC) and ν(CC) phenyl

1030 ν(CC) phenyl 1039, 1115 νa(SiOC) 1175, 1302 T(CH2) 1155, 1178, 1190,

1200, 1225 ν(phenyl)

1255, 1342 ω(CH2) 1427 δ(CH2)

1583, 1603 ν(CC) aromatic

2566 ν(SH) 2860, 2889 νs(CH2) aliphatic 2921, 2965 νa(CH2) aliphatic

3040, 3053 ν(CH) aromatic

S17

References:

[1] Ashworth, F.; Burkhardt, G. N. Effects induced by the phenyl group. Part I. The addition of polar reagents to styrene and the behaviour of the halogenated ethylbenzenes. J Chem Soc 1928, 1791.

[2] Cramer, N. B.; Reddy, S. K.; Cole, M.; Hoyle, C.; Bowman, C. N. Initiation and kinetics of thiol–ene photopolymerizations without photoinitiators. J Polym Sci Pol Chem 2004, 42, 5817–5826.

[3] Sayamol, K.; Knight, A. R. Reactions of Thiyl Radicals .3. Phtochemical Equilibrium in Photolysis of Liquid Disulfide Mixtures. Can J Chem 1968, 46, 999–1003.

[4] Klemm, E.; Sensfuß, S.; Holfter, U.; Schütz, H. Untersuchungen zur linearen thiol-en-photopolymerisation. Makromol Chem 1990, 191, 2403–2411.

[5] Klemm, E.; Sensfuß, S. Investigations on the Mechanism of Autoinitiation in Thiol en-Polymerization. Makromol Chem 1991, 192, 159–164.

[6] Sensfuß, S.; Friedrich, M.; Klemm, E. Untersuchungen zur Thio/En-Polymerisation. Makromol Chem 1991, 192, 2895–2900.

[7] Dsouza, V. T.; Nanjundiah, R.; Baeza, J.; Szmant, H. H. Thiol-Olefin Cooxidation (Toco) Reaction .7. a H-1-NMR Study of Thiol Solvation. J Org Chem 1987, 52, 1720–1725.

[8] Dsouza, V. T.; Iyer, V.; Szmant, H. H. Thiol-Olefin Cooxidation (Toco) Reaction .8. Solvent Effects in the Oxidation of Some Thiols with Molecular-Oxygen. J Org Chem 1987, 52, 1725–1728.

[9] Fouassier, J.-P.; Rabek, J. F., Radiation Curing in Polymer Science and Technology; Kluwer Academic Print on Demand: 1993.

[10] Cramer, N. B.; Scott, J. P.; Bowman, C. N. Photopolymerizations of Thiol-Ene Polymers without Photoinitiators. Macromolecules 2002, 35, 5361–5365.

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Supporting Information for \"Direct Thiol-Ene Photocoating of Polyorganosiloxane Microparticles