Homopolymers as Structure-Driving Agents in Semicrystalline Block Copolymer Micelles

Transcription

1 Supporting information for: Homopolymers as Structure-Driving Agents in Semicrystalline Block Copolymer Micelles Georgios Rizis, Theo G. M. van de Ven*, Adi Eisenberg* Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, Canada, H3A 0B8 and Centre for Self-Assembled Chemical Structures (CSACS).

2 Table SI-1. Molecular characteristics of the amphiphilic block copolymers. Copolymer ID [a] M n (g mol -1 ) [b] [c] Composition (wt.%) M w /M n PCL PEO PAA PEO 45 -b-pcl PEO 45 -b-pcl PEO 45 -b-pcl PEO 45 -b-pcl PEO 114 -b-pcl PAA 33 -b-pcl PAA 57 -b-pcl PEO 45 -b-pcl 37 -b-paa [a] Subscripts give the number average degrees of polymerization. [b] Calculated from 1 H NMR data. [c] Polydispersity indices obtained from gel permeation chromatography; estimated as a non-hydrolyzed PtBA precursor for macromolecules which bear a PAA block. S1

3 Table SI-2. Molecular characteristics of the homo-pcl samples. Homopolymer ID [a] M n (g mol -1 ) [b] M w /M n [c] T m ( o C) [d] PCL PCL PCL PCL PCL [e] Star-PCL [f] 10 [g] Star-PCL [f] - [g] [e] Star-PCL [f] 30 Star-PCL [a] Subscripts give the number average degrees of polymerization. [b] Calculated from 1 H NMR data; inclusive of initiator weight. [c] Polydispersity indices obtained from gel permeation chromatography. [d] Crystallization temperature estimated by differential scanning calorimetry. [e] Commercial sample; molecular characteristics obtained from supplier. [f] Gel permeation chromatography peak outside of calibrated range. [g] Sample is in the form of a clear viscous liquid at ambient temperature. S2

4 Table SI-3. Micellar characteristics for the mixed-corona hybrid sample series. Components: a) PEO 45 -b-pcl 24 b) PAA 57 -b-pcl 47 Component Ratio (wt.%) [a] Homopolymer additive (PCL 10 ) Corona Composition (mol%) [d] a b wt.% [b] mol% [c] PEO PAA Set by mixing 5 g/l polymer solutions of a and b prior to micelle formation. [b] Compared to the combined weight of block copolymers a and b. [c] Compared to the total number of moles of block copolymers a and b. [d] Same as the component ratio expressed in molar percentages. S3

5 Figure SI-1. Representative TEM images showing hybrid spheres and rod-like products hybrid micelles prepared without homopolymer additives. Samples are of 20/80 PAA 57 -b-pcl 47 /PEO 45 -b-pcl 24 mixtures. Scale bar: 250 nm S4

6 Figure SI-2. Stability of PAA 57 -b-pcl 47 spheres towards ph and ionic strength changes. Size distributions by DLS suggest that no size changes occur after 5 days of storage at a ph of 2.5 (top), and show no differences between samples in 100 mm potassium chloride (KCl) and control micelles in pure water (bottom, time: 2 days). S5

7 A B C Figure SI-3. Evolution of the apparent size distribution as a function of time for PAA-b-PCL micelles containing PCL 10 homopolymer. The additive content is 10% (w/w). Changes were evaluated by DLS for (A) PAA 57 -b-pcl 47 and (B) PAA 33 -b-pcl 33 samples in pure water. (C) Size distribution by DLS for PCL 10 - containing samples of PAA 57 -b-pcl 47 after 5 days storage at a ph of 2.5. As compared to the data shown in (A) for an equivalent sample in pure water, note the lower proportion of large aggregates in the size distribution. S6

8 Figure SI-4. TEM images of lamellar products formed from block copolymer spheres containing PCL 10 homopolymer chains (10% w/w). The samples were prepared using PAA 57 -b-pcl 47, with the exception of the sample corresponding to the bottom right side image (PAA 33 -b-pcl 33 ). Many of the products exhibit defects such as those shown in the top row. Thus, edges are not always completely smooth, many lamellae exhibit what appear to be screw dislocations (middle image), and the size is polydisperse. Scale bars: 2 μm (top), 1 μm (bottom). S7

9 Figure SI-5. Representative differential scanning calorimetry curves obtained for homopolymer samples. Curves obtained from both the cooling (top) and heating (bottom) cycles are provided; exothermic processes are positive with respect to the baseline. While a single crystallization peak is observed during the cooling cycle, note the peak splitting that occurs during the melt. S8

10 A B Figure SI-6. Representative differential scanning calorimetry curves obtained for homopolymer-loaded samples of PEO 45 -b-pcl 24. The samples were flash-frozen and freeze-dried from water immediately following self-assembly. Curves obtained from both the cooling (left) and heating (right) cycles are provided; exothermic processes are positive with respect to the baseline. (A) Micelle samples of varying homopolymer content (PCL 10 ); the lower-temperature crystallization peak is ascribed to PEO, which would not crystallize when hydrated. (B) Micelles containing either morphogenically active (PCL 10 ) or inactive (PCL 22 ) additives exhibit similar curves. Mildly depressed melting temperatures are observed in the case of PCL 10. S9

11 Figure SI-7. Representative selected-area electron diffraction patterns obtained for PEO 45 -b-pcl 24 lamellae containing PCL 10 homopolymer chains (10% w/w). To the left of each diffraction pattern is the corresponding TEM image (prepared without staining agents) taken immediately afterwards. The diffracted area is 200 nm in size (central location in each image). The white spot in the top image may due to sample degradation from prolonged exposure to the electron beam. Detailed morphological features are not observed in the absence of staining, which would perturb the diffraction experiment. Scale bars: 200 nm. S10

12 Figure SI-8. Representative AFM height profile images obtained from PEO 45 -b-pcl 24 samples containing PCL 10 homopolymer chains (10% w/w). These images reveal local structural elements composed of aligned rods. The average height of these rod arrays is heterogeneous (roughly 7 nm), while the average lateral center-to-center spacing is 16.7 nm. S11

13 A B Figure SI-9. Homopolymer chain length effects in PEO 45 -b-pcl 24 spheres. (A) Size distributions by DLS obtained 2 days after micelle formation in the presence of homo-pcl additives (wt.% and chain length shown in legend). As the data suggest, the sample shown at top (PCL 14 ) contains the least amount of large aggregate species in solution. Whether containing an equal weight (middle) or equal number of moles (bottom) of the shorter additive PCL 10, the samples exhibit more prominent transformations. (B) TEM images showing ribbon-like aggregates in PEO 45 -b-pcl 24 samples containing 10% (w/w) PCL 22. The samples were aged for 5 weeks, and do not form lamellar products such as those seen in the presence of shorter homo-pcl. Scale bar: 1 μm. S12

14 Figure SI-10. Homopolymer chain length effects in PAA 57 -b-pcl 47 spheres. The homopolymer content is constant at 10% (w/w). The size distributions by DLS compare samples aged for a period of 3 days. The single broadly-distributed species detected in samples containing PCL 22 or PCL 38 is thought to be spheres. Larger aggregates are found in samples containing the shorter PCL 10 or PCL 14 chains. S13

15 A B Figure SI-11. Thermal reversibility of the lamella formation process. The data shown is for PEO 45 -b-pcl 24 micelles containing PCL 10 homopolymer chains (10% w/w). (A) Size distributions obtained using DLS data show a single species at the start of the experiment. After aging for 3 days (Cycle 1), micrometer-sized aggregates are detected, which disappear after a 20-minute incubation at 65 o C, above the melting point of PCL. After the molten sample was left at ambient temperature for 3 additional days, the aggregates form once again. (B) TEM images showing the micrometer-sized aggregates found in the DLS experiments; top and bottom images correspond to transformation cycles 1 and 2, respectively, as also indicated with arrows. Scale bars: 2 μm. S14

16 A B Figure SI-12. Amorphous homo-pcl used with PEO 45 -b-pcl 24 spheres. The homopolymer additive is a 3- arm star sample PCL 6, and exists as a liquid at room temperature (see Table SI-2). (A) Evolution of light scattering intensity with time for PEO 45 -b-pcl 24 spheres containing various homo-pcl additives (constant amount; 10% (w/w)). The sample containing linear chains (PCL 10 ) exhibits substantial transformations. Both the sample containing the amorphous additive and the control exhibit slow morphological ripening at an identical apparent rate; dashed lines are a guide for the eye only. (B) Size distributions by DLS which compare amorphous additive-containing and control micelle samples (corresponding to selected time points from (A): start (left); 1 day (right)). As for the intensity values in (A), these size distributions appear similar, suggesting that the amorphous additive has no effect. S15

17 Figure SI-13. Homopolymer chain architecture effects in PEO 45 -b-pcl 18 spheres. Size distributions by DLS compare samples which containing various homo-pcl additives (constant amount; 10% (w/w)) after a fixed period of time (1 day). The homo-pcl type is indicated in the legend (see Table SI-2 for details). The branched additive PCL 3 is amorphous, and has no effect (compare results with those of control sample). The larger branched additive, PCL 9, is somewhat crystalline; the corresponding sample contains a greater amount of large aggregate species. However, when compared to a linear homo-pcl additive of similar molecular weight, which crystallizes more effectively, the branched additive is markedly less active in promoting the formation of large aggregates from spheres. S16