Morphology–composition–processing relationships in poly(methyl methacrylate)–polytriethylene glycol dimethacrylate shrinkage‐controlled blends

Abstract

An innovative method to control shrinkage in polymer blends, by using N,N-dimethyl-p-toluidine to produce phase separation in an acrylic system, was applied to synthesize polymer blends from polymethyl methacrylate (PMMA) and polytriethylene glycol dimethacrylate (PTEG-DMA). The morphology of several compositions, as analyzed by scanning electron microscopy, reveals microdomains as a function of the specific composition, in contrast to conventional MMA-TEGDMA copolymers synthesized by thermal decomposition of benzoyl peroxide, used here as reference materials. Micro-Raman and DSC analyses were also carried out to support the electron microscopy results as well.

A new approach to network heterogeneity: Polymerization induced phase separation in photo-initiated, free-radical methacrylic systems

“…The later development of the secondary phase can lead to nano/micro-scale cavitation at the interface or within the primary phase. This can compensate for some of the initial volumetric shrinkage occurring in the primary phase, resulting in an overall shrinkage reduction due to phase separation[1, 7, 9]. In the TEGDMA/prepolymer model used here, the linkage between the primary and secondary phases is due to the presence of TEGDMA in both phases as well as physical entanglements involving the prepolymer chains integrated into the bulk homopolymer matrix.…”

Nanostructured Multiphase Polymer Networks

“…In addition, the use of thermo-activated systems in general produces greater internal stresses due to post-polymerization curing contraction effects that can generate poorly controlled micro-/macro-void formation in phase-separated polymers. Alternatively, the use of photopolymerizable systems, either purely free-radical [67,73,74] or free-radical/cationic hybrids [41], has the advantage of room-temperature processing, which limits the temperature rise to the exotherm of the reaction. Moreover, the polymerization can be started on demand after the material is in place.…”

“…Evidence has been presented for the impact of reaction kinetics on macromolecular diffusion and gelation, ultimately dictating final polymer structure and properties in all methacrylate systems, without the addition of prepolymers [58]. Processing conditions such as temperature [73,74], irradiance (for photopolymerizable systems) [36], and initiator concentration [42] are of key importance in determining phase-separation behavior since they directly control reaction kinetics and onset of gelation. In thermally polymerized materials, temperature has two distinct and, more often than not, antagonist effects.…”

“…For example, in many applications, the control of polymerization shrinkage is crucial to the quality and longevity of the polymeric structure, such as in the molded parts and coatings industries, in electronics, and in biomedical fields. One approach that has been used for several years is the induction of phase separation by the addition of pre-polymerized additives [31,32,[72][73][74]. One study has shown that polyethylene glycol dimethacrylate networks modified by the addition of pre-polymerized beads of polymethyl methacrylate show significantly less shrinkage than it would have been predicted [74].…”

“…In purely methacrylate systems, as, for example, in networks modified by the addition of pre-polymerized particles, the phase composition can be modulated by controlling the relative solubility of the particle on the matrix [37, 38; 39, 40], the additive concentration [73], and the potential of the additive to covalently engage with the surrounding network [50,51]. The use of hyperbranched prepolymers has been described as a way to avoid gelation in polymer-dispersed liquid crystals and to control phase formation through the judicious selection of additives of different Tgs at different concentrations [80].…”