Synthesis and enhanced nonlinear optical performance of phthalocyanine indium polymers with electron-donating group porphyrin by efficient energy transfer

In this study, a phthalocyanine indium (InPcOH) and three porphyrin derivatives (Por2a, Por2b, Por2c) were successfully synthesized. Three kinds of novel four-arm star-shaped poly(propylene oxide) (PPO) with core of InPcOH and chain-end of porphyrin derivatives, named InPc-(PPOx-Por2n)4 (n = a-c), were achieved through the InPcOH as initiator by ring-opening polymerization. From fluorescence spectra, InPc-(PPOx-Por2n)4 polymers revealed weaker emission intensity at 704 nm in comparison with InPc-(PPO29)4, proving energy transfer (ET) pathway from Por2a-2c to InPc, which could be established by theoretical study. Due to ET pathway, InPc-(PPOx-Por2n)4 polymers showed stronger nonlinear optical (NLO) performance than InPc-(PPO29)4 polymer. Among InPc-(PPOx-Por2n)4, InPc-(PPO33-Por2b)4 obtained the most outstanding NLO performance exhibiting imaginary third-order susceptibility (Im[χ(3)]) of 6.25 × 10−11 esu, which could ascribe the efficient ET pathway from Por2b to InPc based on the appropriate spatial structure and small energy gap of Por2b. Moreover, the InPc-(PPO33-Por2b)4/polymethyl methacrylate (PMMA) composites were prepared for applying actually, and it displayed a prominent Im[χ(3)] value of 22.4 × 10−11 esu and an outstanding limiting threshold of 0.14 J/cm2. The remarkably enhanced NLO performance exhibited by InPc-(PPO33-Por2b)4/PMMA composites in comparison with that in methyl methacrylate solution prove a feeblish aggregation effect in PMMA matrix, which indicate the great potential of our polymers for real application in NLO field. This research could furnish a novel designing approach in terms of NLO materials that exhibit great performance.