Acrylamide derivatives of bile acids are chosen as a hydrophobic comonomer to copolymerize with acrylamide via reversible addition and fragmentation chain transfer (RAFT) polymerization to afford a series of copolymers of P(AAm-co-CAA). These copolymers exhibit a sharp and reversible insoluble-soluble transition in water upon heating to a mixing temperature (T) related to the upper critical solution temperature (UCST). T of these copolymers can be conveniently tuned to a practical temperature range, around 37 °C for biomedical applications. T rises with increasing molar fraction of the bile acid-based acrylamide and increasing concentration of the aqueous solution of the copolymers. The addition of a natural host molecule β-cyclodextrin lowered the T. The insoluble-soluble transition of the copolymers was also evidenced by dynamic light scattering and transmission electron microscopy. The biocompatible nature of the bile acids and β-cyclodextrins may make these copolymers potentially useful for biomedical applications.

Optical tweezers provide a platform for both manipulating and probing the chemistry of a single polymer molecule tethered between dielectric microspheres. It has been challenging to adapt this technology to organic solvents, in part due to the limited availability of optically trappable materials possessing the necessary diameter and refractive index contrast. Here we report on the development of broadly accessible optical trapping in aqueous and organic solvents that utilizes zinc oxide-silica core/shell microspheres (beads). The addition of a silica shell allows otherwise highly scattering zinc oxide nanoparticles to be stably trapped and readily functionalized. Trapping was observed in water, chloroform, tetrahydrofuran, and ethyl acetate. We demonstrate how these beads can be used to measure the force–extension curves of DNA and poly­(methyl methacrylate) respectively utilizing antibody/antigen complementation or strain-promoted azide/alkyne cycloaddition to form linkages in situ. In the latter, a strong, contiguous chain of covalent bonds is formed between the microspheres; therefore, UV bond photolysis was used to count the number of rupture steps and control for single-molecule link formation. In addition to being trappable in many solvents, ZnO@SiO2 core/shell beads can be used as solid support during harsh synthetic conditions and can be readily prepared in the presence of atmospheric oxygen.

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A series of photoresists was prepared to investigate the effects of flexibility on the properties of thermo-optic waveguide devices.