Automatic continuous online monitoring of polymerization reactions (ACOMP) was used to assess quantitatively the reactivity, average composition drift and distributions, as well as molar mass and intrinsic viscosity evolution of comonomers from the acrylate and methacrylate families during free radical copolymerization. In the latter case, N-methacryloxysuccinimide (MASI) was of chief interest because of its promise as a starting material from which highly tailored polymers can be produced by postpolymerization modifications. It was found that the reactivity ratios of MASI with an acrylate, such as butyl acrylate (BA), were widely separated and comparable to the case of methyl methacrylate (MMA) and BA. In contrast, reactivity ratios for MMA/MASI were closer together, consistent with general trends in the literature for MMA copolymerization with other methacrylates. While this is intuitively reasonable from a chemical point of view, this comprehensive online characterization confirms that at least some predictions about MASI copolymerization behavior can be made using the much wider knowledge base for MMA. The disparity between BA/MASI copolymerization compared to MMA/MASI is also seen in the unusual increase in weight-average molar mass and intrinsic viscosity as conversion increases. This work establishes the precedents and methodologies that can be used as a general tool in MASI-based developments and paves the way toward monitoring ATRP copolymerization of MASI, as well as postpolymerization modifications such as hydrolysis and derivitization.

Automatic continuous online monitoring of polymerization reactions (ACOMP) was applied to free radical copolymerization of acrylic comonomers, whose spectral characteristics are very similar. Determination of the instantaneous concentration of each comonomer during the reaction was made possible by incorporating a full spectrum UV spectrophotometer into the detector train. The working assumption was that a UV spectrum at any instant during conversion is a linear combination of the normalized basis spectra of the comonomers and the copolymer, and that the unknown comonomer concentrations can be found by minimizing the error between measured and computed spectra over many wavelengths, even when spectral differences are small at any given wavelength. Here, the copolymerization of butyl acrylate (BA) and methyl methacrylate (MMA) was monitored under different starting composition ratios. Continuous conversion kinetics, composition drift, and average composition distribution are all found from the data, in addition to the evolution of weight-average intrinsic viscosity and molar mass M w . Reactivity ratios, r mma ) 0.40 ( 0.05 and r ba ) 2.58 (0.1, are close to the averages found from a literature survey over a wide range of conditions. Comonomer conversion results were independently cross-checked by GPC. Increasing the content of BA in the copolymer was found to increase M w , while also leading to a significant increase in chain stiffness. This work sets the stage for extension to copolymerization of three and more comonomers.

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The kinetics and mechanisms involved in the ring-opening metathesis polymerization of 5-norbornene-2-yl acetate (NAc) and cyclooctadiene (COD) in dichloromethane (DCM) were quantified using automatic continuous online monitoring of polymerization (ACOMP). The results yielded time-dependent monomer conversion and the effects of temperature and reactant concentration, evolution of weight-average molecular mass M w, and intrinsic viscosity [η]w. The evolution of the molecular mass was generally consistent with a “living” mechanism in a rapid first phase, where expected target masses for p(NAc) were met, but often revealed a secondary, slight degradative phase. In contrast, p(COD) yielded molar masses far below target values and generally showed a more pronounced degradative phase. These latter two phenomena for p(COD) appear to be symptomatic of a mechanism that shortens chains with concomitant increase in polydispersity. Furthermore, through a combination of M w, viscosity, and concentration dependencies it was deduced that the slow degradative phase for both p(NAc) and p(COD) is due almost entirely to cross-metathesis reactions. A probabilistic analysis for cross-metathesis supports these assertions. Automatic continuous mixing (ACM) was used to measure second virial coefficients and intrinsic viscosity, and these are consistent with polymers having large solvent domains and strong interactions for p(NAc). In a further application, a second addition of monomer during reactions revealed that no observable termination takes place over time. Results were cross-checked by conventional multidetector gel permeation chromatography (GPC). Ultimately, this method should help in the control of reactions to produce highly specific polymers and architectures.