The development of reversible nanostructural associations in graft copolymer architecture has enabled the fabrication of tough polymer electrolyte composites that exhibit autonomous self-healing properties at room temperature. Random copolymers comprising docosyl acrylates (A22) were employed to form network structures in ionic liquids. The behavior of the resulting composites was found to be dictated by associative domain formation and subsequent changes in the intermolecular interactions. Remarkable mechanical properties were achieved without undermining the self-healing capability via adjustments in the chemical structure. This feature is recognizably different considering the conventional trade-off relationship between selfhealing and mechanical properties. Thermal and scattering experiments were conducted to elucidate the structural evolution of the composites. The relative changes in the electrical properties upon mechanical deformation were utilized to realize self-healable strain sensors.

Polymer electrolyte composites (PECs) with ionic liquids (ILs), which are also known as ion gels, are fabricated using random copolymers with crystallizable side chain architecture, and the effects of the side chain interactions that establish the physically crosslinked network structure in the PECs are studied. The free radical copolymerization of docosyl acrylates (A22) and tert-butyl acrylates (tBA) leads to the synthesis of poly(tert-butyl acrylate-r-docosyl acrylate) [poly(tBA-r-A22)] copolymers with a random sequence distribution. The previous studies on semicrystalline copolymer/IL composites have mostly focused on a limited composition range. The poly(tBA-r-A22) random copolymers over a wider range of compositions readily form mechanically tough and ionically conductive PECs upon incorporation of small amounts of IL (approximately 20 wt%). Thin-film transistors with these PECs as an electrolyte gate dielectric exhibit comparable performance to previously reported transistors using PECs with high IL loading. The composition dependence of the side chain crystallization behavior of the random copolymers and the PECs, markedly distinct from that of main chain crystallization, provides a simple and versatile means to design and tune the electrolyte properties for various device applications.

The tunable surface-wetting properties of photosensitive random copolymer mats were used to spatially control the orientations of thin-film block copolymer (BCP) structures. A photosensitive mat was produced via thermal treatment on spin-coated random copolymers of poly(styrene-ran-2-nitrobenzyl methacrylate-ran-glycidyl methacrylate), synthesized via reversible-deactivation radical polymerization. The degree of UV-induced deprotection of the nitrobenzyl esters in the mat was precisely controlled through the amount of UV-irradiation energy imparted to the mat. The resulting polarity switching of the constituents collectively altered the interfacial wetting properties of the mat, and the tunability allowed lamellar or cylinder-forming poly(styrene-b-methyl methacrylate) BCP thin films, applied over the mat, to change the domain orientation from perpendicular to parallel at proper UV exposures. UV irradiation passing through a photomask was capable of generating defined regions of BCP domains with targeted orientations.