Atom transfer radical polymerization and the synthesis of well-defined inorganic/organic hybrid polymeric materials

The goal of the thesis work was to explore the synthetic aspects of the formation of inorganic/organic hybrid polymeric materials. While a variety of inorganic materials were utilized, the unifying theme was the use of atom transfer radical polymerization (ATRP) in the synthesis of the organic segments. In an effort to produce copolymers of poly(dimethylsiloxane) (PDMS) for applications in thermoplastic elastomeric and adhesives technologies, hydrosilylation of commercially available vinyl or hydrosilyl terminal silicone with attachable initiators containing benzyl chloride (BzCl) or 2-bromoisobutyrate (Br iBu) groups was performed. ATRP of styrene, acrylates and methacrylates in the presence of copper(I) bipyridine complexes resulted in ABA triblock copolymers. For styrene polymerization from the benzyl chloride functional PDMS, linear increases in block copolymer molecular weight with monomer conversion were observed. Polydispersity decreased with conversion indicating the addition of organic segments of well-defined structure. In (meth)acrylate ATRP from silicone bearing either the BzCl or BriBu initiating fragments, decreases in measured molecular weight were observed at low conversions. Polymerization of n-butyl acrylate from BriBu-terminal monofunctional PDMS macroinitiators (M_n = 4400 and 19,000), did not show this behavior. Linear increases in molecular weight with conversions and polydispersities below M_w/M_n < 1.2 were obtained. Using the same hydrosilylation techniques, pendant BzCl-functional PDMS macroinitiators were synthesized. ATRP of styrene resulted in the formation of a hybrid graft copolymer. Copolymerization of vinyl monomers with terminal vinyl-functional PDMS macromonomers by the “grafting through” technique resulted in the synthesis of graft copolymers. When the ATRP of methyl methacrylate (MMA) with methacrylate terminal PDMS (PDMS-MA) as well as styrene with a styrene terminal PDMS macromonomer (PDMS-Sty) was initiated from PDMS or polystyrene macroinitiators, the resulting materials were block-graft copolymers. ATRP of MMA with PDMS-MA showed higher rates of incorporation of the silicone relative to the conventional radical polymerization of the same monomers. The ATRP of styrene and acrylates, from silicon wafers containing monolayers of alkyl 2-bromoisobutyres was explored. Controlled increases of polymer layer thickness with both reaction time and molecular weight of untethered chains polymerized in separate, identical experiments was observed. Deactivation of radical species was provided by addition of a copper(II) complex. In the absence of the persistent radical the polystyrene film thickness was 106 rim. compared to the 12 nm. measured for the polymerization with deactivator present. By choice of monomer as well as through functionalization chemistries, the surface hydrophilicity was tuned; water contact angles varied from 119° for a fluoroacrylate to 18° for poly(acrylic acid). Finally, star polymers polymerized by ATRP from multifunctional cyclotriphosphazenes and cyclosiloxanes was examined. Hybrid initiators composed of benzyl halides and ·-halo esters were used in the ATRP of styrene and (meth)acrylates. Kinetic arguments were used to verify that each initiating site on the multifunctional initiators was participating in the ATRP process. ATRP from a hexafunctional initiator facilitated the synthesis of high molecular weight material. (Abstract shortened by UMI.)...