No abstract

Four solid UV-absorptive oligomerspoly(p-ethoxycinnamate) (P2), poly(p-propoxycinnamate) (P3), poly(p-hexyloxycinnamate) (P6), and poly(p-undecyloxycinnamate) (P11)-were condensation polymerized from p-(2-hydroxy-ethoxy) cinnamic acid, p-(3-hydroxy-propoxy) cinnamic acid, p-(6-hydroxy-hexyloxy) cinnamic acid, and p-(11-hydroxy-undecyloxy) cinnamic acid, respectively. The liquid UV-absorptive oligomer, poly(pentaethylene glycol cinnamate) (PPGC), was synthesized through the copolymerization between p-hydroxycinnamic acid and pentaethylene glycol ditosylate. Molecular weights of all five oligomers were in the range of 1600-5500. Absorption profiles of all synthesized polymers indicated UVB absorption characteristics. Upon UVB exposure, trans to cis photoisomerization of all five oligomers was observed, leading to the decrease in their UVB absorption efficiency. No transdermal penetration across a baby mouse skin (Mus musculus Linn.) was detected for the five synthesized oligomers, while the penetration of the standard UVB filter, 2-ethylhexyl-p-methoxycinnamate, through the same skin could be clearly observed. In addition, PPGC, a yellowish water immiscible liquid, showed good solubility in various organic solvents and silicone fluids. PPGC and P3 could be induced into water dispersible nanoparticles using solvent displacement technique.