We report herein the modular synthesis and nanolithographic potential of poly­(dimethylsiloxane-block-methyl methacrylate) (PDMS-b-PMMA) with self-assembled domains approaching sub-10 nm periods. A straightforward and modular coupling strategy, optimized for low molecular weight diblocks and using copper-catalyzed azide–alkyne “click” cycloaddition, was employed to obtain a library of PDMS-b-PMMA and poly­(dimethylsiloxane-block-styrene) (PDMS-b-PS) diblock copolymers. Flory–Huggins interaction parameters, determined from small-angle X-ray scattering experiments, were high for PDMS-b-PMMA (χ ∼ 0.2 at 150 °C), suggesting this diblock copolymer system has promise for sub-10 nm lithographic applications when compared to the corresponding PDMS-b-PS diblock copolymers (χ ∼ 0.1 at 150 °C). Performance evaluation in thin film self-assembly experiments allowed domain periods as small as 12.1 nm to be obtained, which is among the smallest highly ordered nanoscale patterns reported hitherto for thermally annealed materials.

The consequences on certain physical properties of controlled levels of epoxidation of the poly(isoprene) blocks in poly(styrene-b-isoprene) (PS-PI) diblock copolymers and poly(isoprene) (hPI) homopolymers have been studied, where the products after epoxidation are denoted PS-PIxn and hPIxn, respectively. The effective interaction parameters χ eff between the PS and the PIxn blocks were estimated by applying mean-field theory to the lamellar periodicities identified by small-angle X-ray scattering and to the order-to-disorder transition temperatures determined by dynamic mechanical spectroscopy. These results were fit to a binary segment−segment interaction parameter model indicating a nonlinear change in χ eff with percent epoxidation. In contrast, contact angle measurement on hPIxn and lamellar orientations of thin-film PS-PIxn suggest that the surface energy of PIxn increases linearly with epoxidation. This decoupling of bulk and thin-film thermodynamic behaviors is attributed to the different roles that a random copolymer architecture plays in establishing three-dimensional order versus wetting at a two-dimensional surface.

Two high-χ block copolymers, lamella-forming poly(styrene-block-[isoprene-random-epoxyisoprene]) (PS-PEI78, with 78 mol % epoxidation) and lamella-forming poly(4-trimethylsilylstyrene-block-d,l-lactide) (PTMSS-PLA), were used to study three combinations of interfacial neutrality involving at least one neutral interface. PS-PEI78 annealed on a nonpreferential polymer mat (SMG) produced perpendicular lamellae independent of film thickness, indicating a neutral substrate and neutral free surface. In contrast, the presence of only one neutral interface results in the formation of surface topography ("islands" and "holes") with 0.5L0 step heights. PS-PEI78 (neutral free surface) annealed on PS brush (PS block preferential) forms "half" islands and holes. The inverse experiment, PTMSS-PLA (with a PTMSS preferential free surface) annealed on a neutral (or near neutral) substrate surface, also generates 0.5L0 topography. These "half" island and hole structures are stable to extended thermal annealing. PS-PEI78 exposes both blocks at the free surface in contrast to PTMSS-PLA, which exposes just one. All three combinations of interfacial neutrality are explained by the precise balancing of the wetting tendencies of the two blocks. Evolution of the 0.5L0 motifs appears to be facilitated by a preference to form half-period thick nuclei in the initial stages of morphological development.

A new type of physically cross-linked solid polymer electrolyte was demonstrated by using a poly(vinylidene fluoride) (PVDF) homopolymer in a room-temperature ionic liquid. The physical origins of gelation, specific capacitance, ionic conductivity, mechanical property, and capacitive charge modulation in organic thin-film electrochemical transistors were investigated systematically. Gelation occurs through bridging phase-separated homopolymer crystals by polymer chains in the composite electrolyte, thereby forming a rubbery network. The resulting homopolymer ion gels are able to accommodate both outstanding electrical (ionically conductive and capacitive) and mechanical (flexible and free-standing) characteristics of the component ionic liquid and the structuring polymer, respectively. These ion gels were successfully applied to organic thin-film transistors as high-capacitance gate dielectrics. Therefore, these results provide an effective route to generate a highly conductive rubbery polymer electrolyte that can be used in widespread electronic and electrochemical devices.