Combining a strong donor, tris(dodecyloxy)phenyl)-dithieno[3,2-b:2',3'-d]pyrrole, with a strong acceptor, 4,8-dithien-2-yl-2lambda(4)delta(2)-benzo[1,2-c;4,5-c']bis[1,2,5]thiadiazole, has yielded the lowest bandgap, soluble, spray-processable polymer to date. The polymer has access to four different redox states and shows ambipolar behavior in OFETs. Multiple techniques, including transmission/absorption spectroscopy on SWCNTs and reflectance spectroscopy on gold were used to accurately estimate the optical bandgap at 0.5-0.6 eV, which correlates well to theoretical calculations.

A series of poly(4-tert-butylstyrene-block-2-vinylpyridine) [P(tBuSt-b-2VP)] block copolymers (BCPs) with varying volume fractions, molecular weights, and narrow dispersities were synthesized from the commercially available monomers by sequential living anionic polymerization. The copolymers were thoroughly characterized by 1H NMR spectroscopy, size exclusion chromatography, thermal gravimetric analysis, and differential scanning calorimetry (DSC). To examine the effect of the tert-butyl group on the effective interaction parameter (χeff) relative to poly(styrene-block-2-vinylpyridine) [(P(S-b-2VP)], the self-assembly of symmetric copolymers was studied by small-angle X-ray scattering (SAXS) and transmission electron microscopy. Order-to-disorder transitions (ODTs) were identified by both DSC and SAXS on five copolymers, to define the equation χeff(T) = (67.9 ± 1.3)/T – (0.0502 ± 0.0029), which shows a higher enthalpic contribution to χeff than P(S-b-2VP) and approximately 1.5 times larger χeff. This enables a minimum full pitch of 9.6 nm for the symmetric copolymers. Asymmetric copolymers were also examined for bulk self-assembly by SAXS and TEM, exploring both P2VP and PtBuSt cylindrical phases with diameters as small as 6 nm. Feasibility of thin film assembly by thermal annealing was demonstrated for a P2VP cylinder forming BCPs to yield parallel cylinders that were seeded with Pt ions and etched to yield Pt nanowires with diameters as small as 5.8 nm.

We have synthesized a series of poly(4-(2-tetrahydropyranyloxy)styrene) [P(OTHPSt)] homopolymers by living anionic polymerization of the protected monomer (OTHPSt) in tetrahydrofuran at −78 °C, with excellent control over molecular weight and dispersity. The high T g of P(OTHPSt) led to facile purification and isolation of the polymer as a powder. Characterization of the POTHPSt homopolymer by nuclear Overhauser effect spectroscopy confirms the strong preference for the axial position of the relatively sterically demanding alkoxy phenyl group. By sequential monomer addition, a series of low to high molecular weight P(OTHPSt-b-styrene) BCPs with narrow dispersities were synthesized. Quantitative deprotection of the THP groups yielded poly(4-hydroxystyrene-b-styrene) with tunable molecular weights and compositions. The solid-state and melt-phase self-assembly of these diblocks was investigated using synchrotron small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Mean-field theory analysis of the temperature-dependent correlation-hole scattering for a disordered diblock was used to determine the interaction parameter as χ HS/S (T) = (4.39 ± 0.83)/T + (0.109 ± 0.002), which is approximately 4 times larger than that of poly(styrene-b-methyl methacrylate) with the same disproportionately high contribution of entropy to the free energy of mixing.

We have developed a highly versatile universal approach to grow polymer brushes from a variety of substrates with high grafting density by using a single-component system. We describe a random copolymer which consists of an inimer, p-(2-bromoisobutyloylmethyl)styrene (BiBMS), copolymerized with glycidyl methacrylate (GMA) synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization. Thermal cross-linking created a mat that was stable during long exposure in organic solvent even with sonication or during Soxhlet extraction. The absolute bromine density was determined via X-ray photoelectron spectroscopy (XPS) to be 1.86 ± 0.12 Br atoms/nm(3). The ratio of experimental density to calculated absolute initiator density suggests that ~25% of the bromine is lost during cross-linking. Surface-initiated ATRP (SI-ATRP) was used to grow PMMA brushes on the substrate with sacrificial initiator in solution. The brushes were characterized by ellipsometry, XPS, and atomic force microscopy (AFM) to determine thickness, composition, and homogeneity. By correlating the molecular weight of polymer grown in solution with the brush layer thickness, a high grafting density of 0.80 ± 0.06 chains/nm(2) was calculated. By synthesizing the copolymer before cross-linking on the substrate, this single-component approach avoids any issues with blend miscibility as might be present for a multicomponent curable mixture, while resulting in high chain density on a range of substrates.