The copolymerization kinetics of hydroxyethyl methacrylate (HEMA) with either ethylene glycol dimethacrylate (EGDMA) or diethylene glycol dimethacrylate (DEGDMA) in the presence of RAFT controllers is studied using a mathematical model recently developed in our group. The model is based on the concept of multifunctional polymer molecules. The cases of conventional and controlled homopolymerizations of HEMA as well as the RAFT copolymerization of HEMA/EGDMA and HEMA/DEGDMA are addressed and are in good agreement with available experimental data. The bulk/solution version of the model is used as first approximation of the behavior of a RAFT dispersion copolymerization of HEMA/ EGDMA carried out in supercritical carbon dioxide.

Abstract:There is a debate in the literature on whether or not polymer networks synthesized by reversible deactivation radical polymerization (RDRP) processes, such as reversible addition-fragmentation radical transfer (RAFT) copolymerization of vinyl/divinyl monomers, are less heterogeneous than those synthesized by conventional free radical copolymerization (FRP). In this contribution, the syntheses by FRP and RAFT of hydrogels based on 2-hydroxyethylene methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) in supercritical carbon dioxide (scCO 2 ), using Krytox 157 FSL as the dispersing agent, and the properties of the materials produced, are compared. The materials were characterized by differential scanning calorimetry (DSC), swelling index (SI), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Studies on ciprofloxacin loading and release rate from hydrogels were also carried out. The combined results show that the hydrogels synthesized by FRP and RAFT are significantly different, with apparently less heterogeneity present in the materials synthesized by RAFT copolymerization. A ratio of experimental (Mc exp ) to theoretical (Mc theo ) molecular weight between crosslinks was established as a quantitative tool to assess the degree of heterogeneity of a polymer network.

Summary Research in polymer network synthesis is mostly focused on materials with absorbent or controlled‐release properties. They are important in healthcare applications. Free radical copolymerization is the main route to obtain gels, using monomers and crosslinking agents, but the materials produced by this route are highly heterogeneous. These heterogeneities reduce the efficiency of chemical compounds used in controlled‐release applications. Our research is focused on creating new routes of polymer synthesis to reduce these heterogeneities. In this article, we compare gels synthesized by conventional free radical and by reversible addition‐fragmentation chain transfer (RAFT) copolymerization of acrylic monomers in supercritical carbon dioxide. These gels are evaluated for controlled drug delivery applications with vitamin B12. The materials were characterized by scanning electron microscopy (SEM), nitrogen adsorption (BET), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). These characterization techniques allowed us to determine the morphology and texture of each hydrogel and to explain how vitamin release performance is affected by these characteristics of the hydrogel.

A new approach for the production of polystyrene‐blue agave bagasse (BAB) composite materials is presented. In this approach, dried powdered raw BAB is press molded in the presence of a coupling agent based on glycidyl methacrylate (GMA), producing a hybrid material of poly(GMA) grafted onto BAB. The in situ reversible addition‐fragmentation chain transfer (RAFT) polymerization of styrene in presence of this poly(GMA)‐graft‐BAB hybrid material results in a reinforced composite material. These composites are characterized by Fourier‐transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, gel permeation chromatography, scanning electron microscopy, impact test analyses, and dynamic mechanical analysis. The characterization results show that the amount of GMA coupling agent plays a key role in the efficiency of the process, manifested as improvement of the mechanical properties of polystyrene. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47089.

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