Julia L. Lee

The synthesis and characterization of cationic photoinitiators bearing two and three photoactive triarylsulfonium groups in the same molecule

SummaryA novel series of photoinitiators for cationic polymerization have been prepared which bear two and three photoactive triarylsulfonium groups in the same molecule. These compounds have been fully characterized by means of their UV and C-NMR spectra and liquid chromatography as well as by their elemental analyses. The multifunctional triarylsulfonium salts have been compared among themselves and against monofunctional triarylsulfonium salts in the photoinitiated cationic polymerization of dl-limonene dioxide.

Cyclic silyl pinacole ethers

SummaryCyclic silyl pinacole ethers are a new class of difunctional free radical initiators which have been prepared and characterized. On the basis of their first order kinetic rates of dissociation and half-lives, these compounds are high temperature initiators useful generally above 120°C. The unusual difunctional character of these initiators suggests some rather interesting applications for their use.

The synthesis and characterization of polymer-bound diaryliodonium salts and their use in photo and thermally initiated cationic polymerization

SummaryA new method for the synthesis of polymer-bound diaryliodonium salts has been developed which facilitates the preparation of these polymeric initiators. The polymer-bound diaryliodonium salts were used in both photo and thermally initiated cationic polymerizations.

A New Free Radical Approach to the Synthesis of Polydimethylsiloxane-Vinyl Monomer Block Polymers

The platinum catalyzed condensation of bis(silylpinacolate) free radical initiators bearing vinyl groups attached to silicon with α,ω-hydrogen functional polydimethylsiloxane oligomers, i.e., oligomers containing terminal Si-H bonds, leads to the preparation of high molecular weight macroinitiators. The thermolysis of these macroinitiators in the presence of various vinyl monomers provides a direct synthesis of block polymers. Depending on the monomer chosen, simple triblock and/or multisequence block polymers can readily be prepared. Analysis of the products of the block polymerizations using styrene monomer shows that only block polymers are formed. These block polymers display unusual properties such as intense iridescence, reversible stress crazing and solvent dependent mechanical properties. The stress-strain properties of the block polymers have been measured and found to be related to both the relative proportions of the hard and soft blocks and to their respective block lengths. At hard block contents of less than approximately 50%, the block polymers are thermoplastic elastomers while at compositions greater than 50% the block polymers are rubber modified thermoplastics.