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Rapid Modular Synthesis and Processing of Thiol–Ene Functionalized Styrene–Butadiene Block Copolymers

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journal contribution
posted on 10.04.2012, 00:00 by Joshua S. Silverstein, Brendan J. Casey, Mary E. Natoli, Benita J. Dair, Peter Kofinas
Diblock and triblock copolymers of poly­(styrene)-block-poly­(1,2-butadiene) (PS/PB) and PS/PB/PS were modified by photochemical thiol–ene chemistry to process selected functional nanopatterned polymers, with reaction completion in 1 h. PB molecular weight (MW) and thiol–ene ratios were systematically varied based on a model monomer, boc-cysteamine, to determine the efficiency of the reaction. The results demonstrate the polydispersity index (PDI) of modified block copolymers significantly increased when low thiol–ene ratios were employed and sometimes induced gelation of the reacted polymers. Using a 10-fold excess of thiol, functionalizations between 60% and 90% were obtained for amines, carboxylic acids, amides, and a pharmaceutical with a pendant thiol. Differential scanning calorimetry showed a 30–60 °C increase in the glass transition temperature of the daughter polymers. Subsequently, these polymers were spin-coated from solvents found suitable to form self-assembled block copolymer films. The microstructure domain spacing for each polymer was consistent with those originating from the parent polymer. This technique described allows for the formation of nanopatterned block copolymer films with controlled chemistries from a single source material.