Period-doubling behavior in frontal polymerization of multifunctional acrylates

Abstract

Front dynamics in the frontal polymerization of two multifunctional acrylate monomers, 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane ethoxylate triacrylate (TMPTA), with Lupersol 231 [1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane] as the initiator, are studied. In most frontal polymerization systems, the dynamics are associated with a planar front propagating through the sample. However, in some cases, front behavior can be altered: the front becomes nonplanar characterized by complex patterns like spin modes and pulsations. To determine how these periodic and aperiodic modes arise, reactant solutions consisting of HDDA diluted with diethyl phthalate (DEP) and TMPTA diluted with dimethyl sulfoxide (DMSO) were used in the study. In the study we reveal frontal behavior characteristic of period-doubling behavior, a doubling of spin heads that degenerate into an apparently chaotic mode. Also, a pulsating symmetric mode has been observed. These observations have a striking similarity to observations made in studies of self-propagating high-temperature synthesis (SHS) in which the addition of an inert diluent afforded a rich variety of dynamical behavior. The degree of cross-linking has also been found to be a bifurcation parameter. The energy of activation of multifunctional acrylate polymerization is a strong function of the degree of polymerization. By adding a monoacrylate (benzyl acrylate: BzAc), such that the front temperature was invariant, we observed a period-doubling bifurcation sequence through changes in the energy of activation, which has not been previously reported. (c) 1999 American Institute of Physics.

Frontal Polymerization

“…Gray found that the energy of activation of HDDA increased exponentially during the reaction [100]. Applying the steady-state theory of polymerization to Gray's results, Masere et al calculated the effective energy of activation for thermally initiated polymerization (photoinitiation has no energy of activation) by including the energy of activation (E a ) of a typical peroxide [101]. They calculated that E a of HDDA polymerization increased from 80 kJ/mol at 0% conversion (which is the same as that of methacrylic acid) to 140 kJ mol −1 at 80% conversion.…”

“…Masere et al studied fronts with a peroxide initiator at room temperature and used two bifurcation parameters [101]. They added an inert diluent, DMSO, to change the front temperature and observed a variety of modes.…”

Free‐Radical Frontal Copolymerization: The Dependence of the Front Velocity on the Monomer Feed Composition and Reactivity Ratios

“…The studies focused on linear stability analyses, [20,21] convective instabilities, [22,23] and nonlinear dynamics of polymerization waves. [24][25][26][27] Mathematical models of frontal free-radical polymerization were proposed. Two models considered one monomer systems, or homopolymerization, and were solved numerically [28,29] and analytically.…”

Thermal frontal polymerization with a thermally released redox catalyst

“…By reducing the number of propagating radicals, the transition metal reduces the contribution of the energy of activation for the termination step, which increases the effective activation energy. 49,50 To increase the production of free radicals, two reductants were separately tested: benzoin and 6-O-palmitoyl-L-ascorbic acid. The reductant plays an important role in reestablishing the oxidation state.…”

“…Such nonplanar modes of propagation have been the subject of much investigation. 40,[45][46][47][48][49][50][51] The complexity of the front increases with the value of the effective energy of activation. By reducing the number of propagating radicals, the transition metal reduces the contribution of the energy of activation for the termination step, which increases the effective activation energy.…”