Polymerization Kinetics of Poly(2-Hydroxyethyl Methacrylate) Hydrogels and Nanocomposite Materials

Abstract

Hydrogels based on poly(2-hydroxyethyl methacrylate) (PHEMA) are a very important class of biomaterials with several applications mainly in tissue engineering and contacts lenses. Although the polymerization kinetics of HEMA have been investigated in the literature, the development of a model, accounting for both the chemical reaction mechanism and diffusion-controlled phenomena and valid over the whole conversion range, has not appeared so far. Moreover, research on the synthesis of nanocomposite materials based on a polymer matrix has grown rapidly recently because of the improved mechanical, thermal and physical properties provided by the polymer. In this framework, the objective of this research is twofold: to provide a kinetic model for the polymerization of HEMA with accurate estimations of the kinetic and diffusional parameters employed and to investigate the effect of adding various types and amounts of nano-additives to the polymerization rate. In the first part, experimental data are provided from Differential Scanning Calorimetry (DSC) measurements on the variation of the reaction rate with time at several polymerization temperatures. These data are used to accurately evaluate the kinetic rate constants and diffusion-controlled parameters. In the second part, nanocomposites of PHEMA are formed, and the in situ bulk radical polymerization kinetics is investigated with DSC. It was found that the inclusion of nano-montmorillonite results in a slight enhancement of the polymerization rate, while the inverse holds when adding nano-silica. These results are interpreted in terms of noncovalent interactions, such as hydrogen bonding between the monomer and polymer or the nano-additive. X-Ray Diffraction (XRD) and Fourier Transform Infra-Red (FTIR) measurements were carried out to verify the results.

Monomer Conversion, Dimensional Stability, Biaxial Flexural Strength, Ion Release, and Cytotoxicity of Resin-Modified Glass Ionomer Cements Containing Methacrylate-Functionalized Polyacids and Spherical Pre-Reacted Glass Fillers

“…In general, the use of monomers with low glass transition temperature usually results in the high conversion of monomers [38]. Hence, the use of HEMA (T g~− 60 • C) [39] as the primary base methacrylate monomer could help promote the monomer conversion of the material. Additionally, the low viscosity of HEMA monomers may facilitate the mobility of reactive chains, which could increase the degree of monomer conversion [40].…”

Role of Functional Groups in the Monomer Molecule on the Radical Polymerization in the Presence of Graphene Oxide. Polymerization of Hydroxyethyl Acrylate under Isothermal and Non-Isothermal Conditions

“…The latter is significant, especially when polymerization leading to crosslinked structures is investigated, where other techniques that require the dissolution of the formed polymer often fail. Use of DSC in the investigation of the isothermal bulk polymerization of a variety of methacrylate monomers, including the well-studied 2-hydroxy ethyl methacrylate (HEMA), as well as the curing of epoxy resins, has been reported in the references [24][25][26][27][28][29][30][31]. The reason for the use of DSC is that the variation in the reaction rate with time can be measured continuously during the whole reaction.…”

“…The objective of this article is to implement the methodology employed previously for HEMA [31], for a different acrylic, this time, monomer, namely 2-hydroxyethyl acrylate (HEA). Similar to HEMA, this acrylate displays hydrogen bonding responsible for such properties as its high boiling point and water solubility.…”

Determination of Antimicrobial and Antibiofilm Activity of Combined LVX and AMP Impregnated in p(HEMA) Hydrogel

“…Poly hydroxyethyl-methacrylate p(HEMA) is a pH-sensitive polymer, containing anionic hydrogel with a primary alcohol [16] that has hydrophilic and lipophilic moieties; it is non-toxic, transparent, and insoluble in water [17,18]. Furthermore, p(HEMA) offers stable mechanical properties [19]. p(HEMA) is reported to be prepared by additional polymerization (free radical polymerization) of free radical initiator (2.2-azobis (2-methylpropionitrile)) [20].…”