Multi‐Component Kinetic Modeling for Controlling Local Compositions in Thermosensitive Polymers

Abstract

Summary: An explicit terminal copolymerization kinetic model accounting for the copolymerization of up to four different comonomers is developed and applied to model the conversion profiles and local compositional gradients in functionalized PNIPAM‐based polymer and hydrogel systems. The kinetics of the functional comonomer(s) have a large influence on both the mole fraction and chain distribution of functional groups in polymers. Strategies are developed to synthesize polymers with uniform compositions by applying semi‐batch techniques or via copolymerization of multiple monomers with the same target functionality but with divergent reactivities relative to NIPAM. Synthetic protocols are also designed to maximize the compositional uniformity and randomness of ampholytic polymers.Instantaneous mole fractions of monomers in polymers as a function of the overall monomer conversion for the copolymerizations of NIPAM, MBA, and two functional monomers: MMA and acrylamide.magnified imageInstantaneous mole fractions of monomers in polymers as a function of the overall monomer conversion for the copolymerizations of NIPAM, MBA, and two functional monomers: MMA and acrylamide.

Hydroxyl functionalized thermosensitive microgels with quadratic crosslinking density distribution

“…As seen here, the monodispersity was high particularly for the microgel obtained by PEPTA and some size distribution was observed for the microgels produced by using GDMA and PETA. The critical importance of polymerization kinetics on the network structure of thermosensitive polymers was shown by Hoare and McLean [40]. To have and idea on the correlation between hydrophilicity of the crosslinking agent and polymerization kinetics, the variation of average hydrodynamic diameter of forming particles with the polymerization time was followed by DLS in the dispersion polymerizations performed with different crosslinking agents.…”

Characterizing charge and crosslinker distributions in polyelectrolyte microgels

“…Based on these initial observations and kinetic parameters reported in the literature, we developed a model to theoretically predict the microstructure of microgels according to the copolymerization kinetics of the constituent co-monomers [77]. In this model, based on the terminal copolymerization kinetics approach developed by Hamielec et al [78], monomer consumption rates are calculated based on the reactivity ratios between each pair of monomers used in the microgel preparation, the initial propagation rates for the homopolymerization of each of the monomers, and the composition of the initial monomer mixture, all of which are experimentally measurable parameters.…”

Kinetic Prediction of Functional Group Distributions in Thermosensitive Microgels

“…12 In this work, the observed link between copolymerization kinetics and radial functional group distributions in microgels is applied together with this kinetic model to predict functional group distributions in microgels. Such modeling work is also a key first step in the development of strategies to theoretically predict microgel microstructures under a range of different environmental conditions.…”