Synthesis of Polystyrene-block-poly(4-(phenylethynyl)styrene) (PS-b-PPES) Diblock Copolymers as Precursors for Cobalt-containing Materials

Block copolymers consist of two or more homopolymer units linked by a covalent bond. They have attracted great research interest because they can microphase separate to form highly ordered nanostructures. The well-defined nanoscale metal-polymer hybrid materials can be formed through self-assembly and phase separation of alkyne-functional polymers with metal species that can react with the alkyne groups, which may have potential applications for memory storage, energy storage, and biomedical equipment. The focus of this thesis is the synthesis of polystyrene-block-poly(4-(phenylethynyl)styrene) (PS-b-PPES) diblock copolymers as precursors for cobalt-containing materials.;Polystyrene-block-poly(4-(phenylethynyl)styrene) (PS- b-PPES) diblock copolymers were synthesized at a variety of PS/PPES ratios by reversible addition-fragmentation chain transfer (RAFT) polymerization. Macro chain transfer agent (mCTA) was achieved by RAFT polymerization of polystyrene (PS) with chain transfer agent (CTA), S-alpha(Methoxycarbonyl)phenylmethyl dithiobenzoate (MCPDB). PS-b-PPES diblock copolymers were subsequently prepared by RAFT polymerization of 4-(phenylethynyl)styrene (4-PES) with the PS-mCTA. Copolymer samples were treated with one equivalent of cobalt carbonyl (Co2(CO)8) compound per alkyne unit at room temperature to form cobalt-polymer hybrid materials.;Proton nuclear magnetic resonance (1H NMR) spectroscopy and gel permeation chromatography (GPC) were applied to analyze the PS-mCTA and diblock copolymer products. The miscibility of poly(4-(phenylethynyl)styrene) (PPES) with PS in diblock copolymers with different compositions was characterized by differential scanning calorimetry (DSC). The loss of CO from cobalt-copolymer adducts was monitored by IR spectroscopy after heating in bulk at 110°C for 24 hours. Transmission electron microscopy (TEM) was used to investigate the phase separation of the self-assembled cobalt-polymer hybrid materials, which appears to form cylindrical morphologies for different compositions (PS89-PPES23[Co2(CO)6]21 , PS89-PPES41[Co2(CO)6] 37, PS125-PPES51[Co2(CO)6] 46, and PS125-PPES125[Co2(CO) 6]112). Increasing the length of PS and PPES blocks leads to an increase in the size of the each domain. In addition, PS89-PPES 23[Co2(CO)6]21 and PS125-PPES 125[Co2(CO)6]112 both form cylinders, but for PS89-PPES23[Co2(CO)6] 21, polystyrene is the majority domain; and for PS125-PPES 125[Co2(CO)6]112, polystyrene is the minority domain.