No abstract

Dual‐functional monomers consist of two distinctly different functional groups that enable chemical versatility. The most readily available epoxy‐methacrylate dual‐functional monomer is glycidyl methacrylate (GMA). In an effort to produce bio‐based, aromatic complements to GMA, asymmetric phenolic diols (vanillyl alcohol, syringyl alcohol, gastrodigenin, and tyrosol) were identified and selectively epoxidized at the aromatic hydroxyl followed by subsequent esterification at the aliphatic hydroxyl to prepare dual functional monomers, vanillyl alcohol epoxy‐methacrylate (VAEM), syringyl alcohol epoxy‐methacrylate (SAEM), gastrodigenin epoxy‐methacrylate (GDEM), and tyrosol epoxy‐methacrylate (TEM). These monomers are viable platforms for a multitude of applications due to their unique chemical functionalities. VAEM, SAEM, GDEM, and TEM were homopolymerized individually to produce aromatic, bio‐based epoxy‐functional thermoplastics analogous to poly(GMA). The molecular weight distributions and thermal properties of each polymer were evaluated, as were the surface characteristics of flow‐coated thin films from these polymers. Most of the newly prepared epoxy‐functional thermoplastics exhibited increased thermal stability (initial decomposition temperatures >260 °C in air) relative to poly(GMA), while retaining similar glass transition temperatures (~ 65 °C) and surface energies (~ 53 mJ m−2); thus, these materials could be substituted for poly(GMA) and enable use in higher‐temperature applications. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 673–682

Sun protection is a global concern, and maximizing sunscreen stability and efficacy depends partially on the prevention of UV filters recrystallization. We aimed to study the efficacy of hydrophobic solubilizers in preventing the recrystallization of solid hydrophobic UV filters in predissolutions, sunscreen formulations, and during simulated human use. Recrystallization of UV filters induced by ultrasonication, temperature variation, or simulated human application was analyzed by different methods. Maximum solubility of UV filters in solubilizers was determined. Surprisingly, the best solubilizer was not necessarily the best solvent to prevent recrystallization, suggesting there are different forces controlling these phenomena. Hydrophobic solubilizers tend to perform better than ethanol in predissolutions, but the presence of other components in final products may change their performance. Results suggest that some UV filters tend to form liquid clusters, which may behave as crystals and affect the desired even distribution of UV filters on the skin. UV filters were also found to respond differently to Hansen Solubility Parameters. Scanning electron microscopy supports the fact that recrystallization upon sunscreen application is an issue to be tested during development. A timesaving method to predict recrystallization of UV filters in clear systems was developed and is presented as a tool to enhance the efficacy of sunscreens.

The customization of polymer networks can be made possible via dual-functional monomers, molecules characterized by two different reactive substituents that allow for versatile methods of polymerization. The dual-functional, epoxymethacrylate monomers, glycidyl methacrylate (GMA), and vanillyl alcohol epoxy-methacrylate (VAEM), were polymerized with methyl methacrylate (MMA) via reversible addition-fragmentation chain transfer (RAFT) polymerization to form low molecular weight (~10-20 kDa) epoxy-functional thermoplastic copolymers, poly(VAEM-coMMA), and poly(GMA-coMMA). The copolymers were blended at 5 wt% into an epoxy resin system containing EPON Resin 828 and EPIKURE W Curing Agent and cured thermally to create unique interpenetrating polymer networks (IPNs). The resulting IPNs were compared to the cured neat resin and evaluated for thermal and mechanical properties, where maintained thermal properties and enhancements of stiffness and toughness were demonstrated.