M. Penco

Chiral functional polymers as catalysts in phase transfer reactions

Abstract The preparation of linear and crosslinked functional polymers designed for catalytic applications in phase transfer reactions is reported. Polymers containing either quaternary ammonium groups or oligoether moieties (glymes and crown ethers) in the side chain, experiencing a prevailing chirality, are described. Procedures based on direct polymerization of a chiral monomer with a functional comonomer, chemical transformation of preformed chiral copolymers and the use of optically active porogens have been adopted for the formulation of catalytically active polymers. Reduction of prochiral alkyl ketones, alkylation of phenylacetonitrile and oxidation of racemic alcohols have been taken as test reactions for catalyst activity, in terms of chemical kinetics and stereochemical control. In spite of the improved chemical stability and maintenance of the chiral integrity, the polymeric catalysts investigated do not seem able to exert enantio-selective discrimination on any of the prochiral or chiral substrates examined.

EFFECT ON STRUCTURAL RELAXATION OF THE POLY(METHYL‐METHACRYLATE) COPOLYMERS CHAIN FLEXIBILITY

The structural relaxation of PMMA copolymers with different chain flexibility has been studied by DSC with two classical procedures, namely: the rate of cooling and the isothermal approaches. The apparent activation energy of enthalpy relaxation was evaluated from the dependence of the glass transition temperature on the cooling rate while a comparison of the apparent relaxation rates was appraised from the enthalpy loss by annealing the different samples at the same level of undercooling (Ta = Tg−18 °C).