SIDE-CHAIN PENDANT NONLINEAR OPTICALLY-ACTIVE POLYMERS SYNTHESIZED BYGRAFTING REACTIONS ON MALEIC-ANHYDRIDE COPOLYMERS

The synthesis of well defined, high molecular weight polymers for non- linear optical (NLO) applications has been carried out in an effort to improve the film properties of waveguides fabricated from these mater ials. Free radical methods of polymerisation result in molecular weigh t limitations due to the chain transfer nature of the NLO active chrom ophores, and therefore, in order to prepare a high molecular weight po lymer, a post polymerisation grafting method was chosen to incorporate side chain pendant chromophores onto a preformed polymer. Alcoholysis of anhydride copolymers resulted in chromophore incorporation levels of up to 90% of available reactive sites. Additional branching of the linear anhydride prepolymers was also carried out using polytetrahydro furan but this was not shown to improve the mechanical properties of t he fabricated films. Since the anhydride opens to an ester and an acid , in order to reduce the ionic content of the final polymer, further r eaction of the generated carboxylic acid group was attempted, resultin g in partial diester formation, and an improvement in film quality. El ectrical field poling at temperatures close to the glass transition wa s only successful at low electrical field strengths, allowing electroo ptic coefficients of values of up to 2.4 pm/V at a poling field of 80 V/mu m to be obtained.