Pulsed laser polymerizations coupled with size exclusion chromatography (PLP-SEC) and NMR analyses were performed to determine radical kinetic parameters for BMA/HEA, with a focus on the effect of solvent choice and H-bonding on both copolymer composition and copolymer-averaged propagation rate coefficients.

Experimental data obtained via pulsed laser polymerization are used to distinguish the influence of H-bonding on kinetic chain-growth parameters from that of side-chain heteroatoms.

thermoset complex copolymers, a change driven by the need to maintain relatively low solution viscosity for efficient application of the coating while greatly reducing the solvent level in the formulation. [1][2][3] Control of both composition and chain length of these new materials is paramount to ensure that the reactive groups, introduced by utilizing (meth)acrylates with glycidyl, hydroxyl, and/or carboxylic acid functionality, are uniform across the chain distribution while specific target qualities (e.g., resin refractive index, glass transition temperature, solution viscosity) are maintained. [4,5] A generalized simulation framework provides a means to systematically capture the knowledge required to develop and efficiently maintain a diverse portfolio of products. Modeling strategies, such as the method of moments pioneered by Ray, [6] are required for the simultaneous modeling of copolymer composition and polymer MM averages during radical copolymerization. [7][8][9] Ray and co-workers combined the specialized modeling strategies required to represent polymer structure into a simulation package, POLYRED, [10,11] that was applied for the representation of solution, [7] suspension, [12] and emulsion [13] radical copolymerization, among other chemistries. The challenge is to develop a modeling platform that can capture the complexities of current recipes and be easily adapted and extended to include new monomers and reaction conditions.A firm knowledge of the basic set of radical polymerization mechanisms and the associated kinetic coefficients is required. The application of specialized experimental techniques has led to the understanding of "family-type" behavior; i.e., that all methacrylate monomers show generalized trends in rate coefficients that are distinctly different than those seen for acrylate monomers or styrene. Propagation kinetics, for example, of styrene, [14] alkyl and functional methacrylates, [15,16] and alkyl acrylates [17,18] are now well understood after application of the IUPAC recommended pulsed laser polymerization-size exclusion chromatography (PLP-SEC) technique. Understanding of radical termination kinetics has also been generalized, with knowledge gained from PLP techniques coupled with electron paramagnetic resonance (EPR) spectroscopy to monitor radical concentrations, as summarized in a recent update from Buback et al. [19] With knowledge of initiation, propagation, and termination kinetics, monomer consumption rates and associated heat releases can be calculated. Equally important, knowledge of the basic radical polymerization kinetics has led to better Semibatch CopolymerizationNonfunctional monomer feedstocks containing alkyl meth(acrylate) components such as butyl acrylate (BA) and butyl methacrylate (BMA) are replaced or augmented with functional monomers such as 2-hydroxyethyl methacrylate (HEMA) and 2-hydroxyethyl acrylate (HEA) to produce reactive polymer chains of lowered molar mass for application in solvent-borne automotive coatings. The introduction of such polar ...

Abstract:The radical copolymerization of butyl acrylate (BA) and 2-hydroxyethyl acrylate (HEA) was investigated under batch and semi-batch operations, with a focus on the influence of hydrogen-bonding on acrylate backbiting. The effect of hydrogen bonding on HEA to BA relative incorporation rates during copolymerization, previously seen in low-conversion kinetic studies, was also observed under high-conversion semi-batch conditions. However, overall reaction rates (as indicated by free monomer concentrations), polymer molar masses, and branching levels did not vary as copolymer HEA content was increased from 0 to 40 wt % in the semi-batch system. In contrast, introduction of a H-bonding solvent, n-pentanol, led to an observable decrease in branching levels, and branching levels were also reduced in batch (co)polymerizations with HEA. These differences can be attributed to the low levels of unreacted HEA in the starved-feed semi-batch system.

Pulsed-laser polymerization combined with polymer analysis by NMR and size-exclusion chromatography is used to study the radical copolymerization kinetics of isoprene (IP) with glycidyl methacrylate (GMA). The copolymer is characterized by a close-to-alternating microstructure, with the addition of IP leading to a significant decrease in the composition-averaged propagation rate coefficient. A rigorous fitting strategy is developed to fit a mixed penultimate model to the data, with the selectivity of the IP, but not the GMA, macroradical dependent on the penultimate unit.