Supporting Information

for

Advanced Materials, adma.200700107

© Wiley-VCH 200769451 Weinheim, Germany

1

Supporting Information for:

Electrospinning pH-Responsive Block Copolymer Nano-Fibers

Authors: Linge Wang et al.

Figure S1. Reaction scheme for the synthesis of the monodisperse PMMA-b-PDEA-b-PMMA triblock copolymer via Group Transfer Polymerization. The ‘X’ featured at the centre of the polymer chain represents the bifunctional initiator moiety, bis(methoxy-trimethylsiloxymethylene) cyclohexane (CHMTS).

Figure S2. Schematic diagram of three different length scales of the chemical and physiological changes of the triblock copolymer under acidic & basic conditions.

2

Figure S3. Schematic diagram of the electrospinning setup.

Figure S4. Digital Camera and SEM images of highly aligned electrospun fibers, where the diameter of the aluminium wire drum was 8 cm (twice larger than that for collecting normal fibers) and the rotating speed was set at 600 rpm.

Figure S5. Schematic diagram of the annealing setup

3

Figure S6. SAXS data during annealing (in THF at 25 °C) of electrospun fibers processed from a 35 wt% PMMA-b-PDEA-b-PMMA/THF solution. The time resolved SAXS experiments were performed using NanoSTAR equipment and the data sets have been translated along the intensity for clarity. Selected 2D SAXS patterns have also been included.

Annealing experiments were also undertaken on a Bruker AXS NanoStar laboratory SAXS instrument equipped with a 2D position-sensitive gas detector (Hi-Star, Siemens AXS) and a CuK radiation source ( = 1.54 Å). Data were acquired using a sample-detector distance of 1.045 m over a q-range 0.01-0.2 Å-1. The annealing temperature was held at either 25 ºC (annealing in THF) or 30 ºC (annealing in DMF). Time-resolved SAXS patterns were collected at 5 minutes per frame for a total of 14 frames during the annealing process. The annealing experiment (using THF) was repeated using the NanoSTAR SAXS equipment. Due to the temperature being 25 °C (5 °C higher than that of the experiment undertaken at the ESRF) the annealing mechanism proceeded slightly faster, as shown in Figure S6. After 40 minutes the polymer chains were fully dissolved and the SAXS image resembled that of a solution (i.e. no peak observed). When these fully annealed fibers were removed from the THF atmosphere and held in air for approximately 15 minutes the solvent was allowed to evaporate and the peak in the SAXS data reappeared at the same q value (~0.024 Å-1). When replaced into the annealing vessel, the SAXS peak again diminished as the polymer chains dissolved. The data from this experiment (Figure S6) were similar to the data discussed in the manuscript (Figure 2), as the mechanism is identical in both cases, with the only difference arising from the slightly higher temperature which increased the polymer chain mobility, and therefore, the ordering/ dissolution proceeded faster.

4

Figure S7. SAXS data and SEM micrographs of PMMA-b-PDEA-b-PMMA electrospun fibers during the annealing process (in DMF at 30 °C) processed from a 35 wt% copolymer/THF solution. The time resolved SAXS experiments were performed using NanoSTAR equipment and the data sets have been translated along the intensity axis for clarity.

The SAXS data from the fibers annealed in DMF (Figure S7) have shown that the process was similar to THF annealing, where this time the copolymer chains reorganized from a random morphology to a regular structure (gel-form structure) during the first 25 minutes (as the peak appears in the SAXS data and its intensity increases with time). After 25 minutes the peak decreased in intensity and became broader as the polymer network began to dissolve. The only major difference between the two annealing systems is that the DMF process was much slower than that of THF, even though the annealing temperature was set at 30 °C. This is because DMF has a lower vapor pressure than THF and 25 minutes were necessary to get from dry fibers to the gel-form structure compared to the 10 minutes required when using THF at 25 °C.

5

Figure S8. q values of the electrospun fibers after 5 minutes annealing (in THF at 25 C)for different solvent mixture ratios (a) and different w/w % polymer concentrations in THF (b). (c) shows the 1D integrated SAXS data taken from the 2D SAXS image of the fibers annealed for 5 minutes (inset), which was electrospun from the 35 wt% copolymer solutions with solvent mixture of THF/DMF at 40/60.

The annealing process in THF is similar for fibers fabricated from different electrospinning conditions. As shown in Figure S8, the q values of the annealed fibers processed from different cosolvent ratios and polymer solution concentrations were very similar. This is due to the fact that the fibers have been electrospun from the same polymer and so the length scale between PMMA aggregates will be the same after annealing (because the material has the same molecular weight and volume fraction of copolymer components).