High Tg NLO-polymers by functionalization of reactive precursors

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Abstract
A new copolymer system with high, but still variable glass-transition temperatures was synthesized. The fixation of various NLO-chromophores is performed after the radical is performed after the radical copolymerization by a polymer analogous reaction. This was accomplished by copolymerizing various N-substituted maleimides with methylvinyl- or vinylisocyanate, so that a polymer with a 1:1 composition of the two monomers and reactive isocynate side-groups is obtained. With different substituents attached to the imide-ring, Tg can be adjusted between 100 and 200 degrees C. Two effects of the substituent at the imide-nitrogen are observed. Bulky gorups reduce the mobility of the chain and lead to high Tg values. A similar tendency is found for smaller less flexible substituents. In this case the intermolecular forces by hydrogen-bonding (urethanes) contibute ot the effects for high Tg's. A variety of different NLO-chromopores can be fixed on the polymer backbone by reaction of a hydroxyalkyl-spacer with the isocyanates, so that a urethane linkage between the chromophore and the polymer is formed. Based on the experience obtained with this first class of NLO-materials, new functionalized polymers were prepared. In order to further increase the Tg-values, while keeping a good processability (solubility), chemical modifications of the spin-coated polymer were prepared. In order to further increase the Tg-values, while keeping a good processablility (solubility), chemical modifications of the spin-coated polymer were performed. Monomers functionalized with tertiary butyl groups (esters or carbonates) allow it, to split off isobutene from the final (and processed) polymer, thereby reducing its solubility and increasing its Tg-value.

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