Synthesis and Nonlinear Optical Characteristics of Chromophore-Functionalized Polymers Having Chromophore-Centered Hydrogen-Bonding and Crosslinking Groups

Abstract

ABSTRACTIn this study, we report the synthesis and characterization of a new, systematically designed class of second-order NLO polymers in which the appended chromophoric substituent is modified (hydroxylated) to allow direct chromophore involvement in hydrogen-bonding and crosslinking. Thus, the glassy polymer poly(p-hydroxystyrene) has been functionalized to varying levels with the N-(3-hydroxy-4-nitrophenyl)-(S)-prolinoxy (HNPP) high-β chromophore. The time-dependent second harmonic generation characteristics of thin films of this material have been studied at λ = 1.064 μm as a function of chromophore functionalization level, hydrogen-bonding capacity, and thermal crosslinking. These materials are found to possess high d33 values (up to 34 × 10−9 esu) and long characteristic SHG decay times (longer than a year). Analysis of the decay of the second harmonic signal shows that increasing hydrogen-bonding density substantially increases relaxation times; it is further shown that introduction of crosslinks is yet more effective in imparting SHG temporal stability to these polymeric nonlinear optical materials.