Copolymer Sequence Regulation Enabled by Reactivity Ratio Fingerprints via Machine Learning.

The determination of reactivity ratios is simplified by using an excess of one monomer (M1) at a time large enough that the copolymers will have a very small content of the other monomer (M2). In this case chain propagation takes place almost exclusively by addition to polymer radicals with a terminal M1‐unit (P) and monomer consumption by propagation of P may be neglected. One reactivity ratio (r1) is obtained from monomer conversions by means of a simple integrated equation which is valid up to high conversions. A calculation is proposed in order to account for the neglected propagation via P. The other reactivity ratio (r2) is obtained from copolymerizations with excess M2.As the new method uses an integrated form of the MAYO equation it permits the determination of monomer conversions directly by gas chromatography of unreacted monomers. Thus, if desired, analysis of copolymers can be avoided. The gas chromatographic method has been tested with the radical copolymerization of styrene and methyl methacrylate.In ternary and quaternary copolymerizations the new method offers particular advantages.

This paper proposes a new method for calculating the monomer reactivity ratios for binary copolymerization based on the terminal model. The original optimization method involves a numerical integration algorithm and an optimization algorithm based on k-nearest neighbour non-parametric regression. The calculation method has been tested on simulated and experimental data sets, at low (<10%), medium (10–35%) and high conversions (>40%), yielding reactivity ratios in a good agreement with the usual methods such as intersection, Fineman–Ross, reverse Fineman–Ross, Kelen–Tüdös, extended Kelen–Tüdös and the error in variable method. The experimental data sets used in this comparative analysis are copolymerization of 2-(N-phthalimido) ethyl acrylate with 1-vinyl-2-pyrolidone for low conversion, copolymerization of isoprene with glycidyl methacrylate for medium conversion and copolymerization of N-isopropylacrylamide with N,N-dimethylacrylamide for high conversion. Also, the possibility to estimate experimental errors from a single experimental data set formed by n experimental data is shown.

Copolymers of acrylamide ( AM ) and acrylic acid ( AA) were prepared by precipitation polymerization method at 65 °C in the ethyl acetate as solvent. Copolymer composition was determined by elemental analysis. Monomer reactivity ratios were determined in low conversions. Mayo-Lewis, Finemann-Ross, Inverted Finemann-Ross, Ezrielev-Brokhina-Roskin, Kelen-Tudos, Extended Kelen-Tudos and Mao-Huglin methods, as linear methods, and Tidwell-Mortimer, as nonlinear method, were applied to calculate rAM and rAA r reactivity ratios. Monomer reactivity ratios of AM and AA were obtained 0.46 and 0.28, respectively. Comparing of reactivity ratios of AM and AA in this work by other solvents showed that hydrogen bonding and ionic strength are important parameters that can affect the reactivity ratios of monomers. Moreover, microstructure of copolymers was determined using reactivity ratios and conditional probability based on the kinetic model for free-radical polymerization.

Copolymerization is a powerful tool for tuning the properties of synthetic polymers. In chain-growth polymerization, copolymer microstructure is controlled by the relative reactivity of comonomers, quantified by copolymer reactivity ratios. Yet, the complex macromolecular reactivity captured by reactivity ratios precludes the prediction of the resultant microstructures by intuition, and the established theory to understand reactivity ratios (i.e., Q-e scheme) has not been updated substantially since the development of quantum mechanics. Here, we combine modern computation, data science, and experimental validation to gain a detailed structure–reactivity understanding of the electronic, energetic, and steric parameters that govern comonomer reactivity. Using >450 reactivity ratios identified from primary literature sources, a combination of parametrization from density functional theory and data science methods identified discrete structure–reactivity relationships in free radical copolymerization. We demonstrate that the electronics of the radical species and the sterics of the monomers, neither of which were captured in the previous Q-e scheme, are pivotal to understanding the copolymerization reactivity. Experimentally measured reactivity ratios of a previously unstudied monomer combination validated the models, demonstrating the potential predictive power of this work to understand the comonomer sequence a priori. This work provides a framework to understand polymer microstructure from first-principles by relating specific and interpretable attributes of monomer structure to comonomer reactivity.

Copolymers of poly( n-alkyl acrylates): synthesis, characterization, and monomer reactivity ratios

Dimethyl meta-isopropenyl benzyl isocyanate (TMI®) is a bifunctional monomer with an unsaturation and an isocyanate group. Bulk copolymerizations of TMI with styrene, methyl methacrylate, and n-butyl acrylate were investigated. Polymerizations were carried out to low conversions in sealed test tubes at 70°C. The copolymer composition was determined using Fourier transform infrared (FTIR) spectroscopy. The data were analyzed using the terminal, as well as restricted penultimate, model of copolymerization. The method of Kelen-Tudos was used to calculate the reactivity ratios according to the terminal model. A nonlinear regression analysis was also carried out. Low reactivity ratio values for TMI were obtained for the copolymerizations with styrene and methyl methacrylate as a result of the inability of TMI to undergo homopolymerization. The value was higher for the copolymerization with n-butyl acrylate. Composition diagrams were generated, and the range of TMI concentration in the monomer charge for the preferential incorporation of TMI in the copolymer was identified. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 559–568, 1998

The new copolymers from different feed compositions of glycidyl methacrylate (GMA) and tetrahydrofurfuryl acrylate (THFA) were synthesized using free radical polymerization in toluene at 70±1 °C using benzoyl peroxide (BPO) as initiator. The polymers were characterized by 1H NMR, 13C NMR and FTIR spectroscopic techniques. The polydispersities of the copolymers suggest a strong tendency for chain termination by disproportionation. The glass transition temperature of the copolymers increases with increase in GMA content. The thermal stability of the copolymers increases with increase in THFA content. The copolymer compositions were determined using 1H NMR analysis. Reactivity ratios for GMA and THFA as determined by the Mao-Huglin method were r1=0.379 and r2=0.266. The results showed that all these copolymerizations are strictly linear systems describable by the Mayo-Lewis equation based on the terminal model and that accurate reactivity ratio data can be obtained.

The copolymerization reactivity ratios for 2-ethoxyethyl methacrylate (EOEMA) with dodecyl methacrylate (DDMA) or styrene (ST) were estimated. Polymerization was performed by using tert-butyl peroxy-2-ethylhexanoate (0.01 mol dm−3) as initiator, isothermally (70 °C) to low conversions (< 10 wt.%) in a wide range of copolymer compositions (every 10 mol-% steps). For the DDMA/EOEMA copolymerization both monomers prefer to react with EOEMA: r (DDMA) = 0.82 and r (EOEMA) = 1.26 with r (DDMA) × r (EOEMA) = 1, which results in the random copolymerization. For the ST/EOEMA copolymerization reactivity ratios are r (ST) = 0.59 and r (EOEMA) = 0.49 indicating a higher reactivity with opposite monomer, while the alternation tendency is not highly pronounced. The probabilities for formations of dyad and triad monomer sequences in dependence on monomer compositions were calculated from the obtained reactivity ratios. With the share increase of ST or DDMA in copolymers surface properties changed from hydrophilic to hydrophobic. Glass transition temperature of copolymer increased with the increase of ST and decrease of DDMA. The molar mass distribution and thermal degradation of synthesized copolymers were also determined and discussed. The reactivity ratios enable optimization of copolymer properties for a given application as polyelectrolytes, drug delivery systems and multifunctional additives for improvement of rheological properties of lubricating oils.

On the determination of monomer reactivities in copolymerization

The reactivity ratios for the copolymerization of a first‐generation dendronized monomer with styrene and different acrylates are determined. The obtained ratios as well as the copolymer compositions that can be expected are discussed in detail. The influence of the dendron on the polymerization potential of the monomer is estimated by comparing its reactivity to those of linear systems as well as using higher generations of the dendronized monomer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

The new acrylic monomer 4-benzyloxycarbonyl phenyl acrylate (BCPA) was synthesized and copolymerized with methyl methacrylate (MMA) in ethyl methyl ketone at 70±1°C using benzoyl peroxide as a free radical initiator. The copolymers were characterized by FT-IR, 1H-NMR and 13C-NMR spectroscopic techniques. The compositions of the copolymers were determined by 1H-NMR analysis. The reactivity ratios of the monomers were determined using the Fineman–Ross (r1=0.6085 and r2=1.7251), Kelen–Tüdös (r1=0.6085 and r2=1.7276), Ext. Kelen–Tüdös (r1=0.6083 and r2=1.7963) and nonlinear error-in-variables model methods (r1=0.6627 and r2=1.7858). The solubilities of the polymers were tested in various polar and non-polar solvents. The elemental analysis was determined by a Perkin–Elmer C–H analyzer. The molecular weights (M¯ w and M¯ n) of the copolymers were determined by gel permeation chromatography. Thermogravimetric analysis of the polymers reveals that the thermal stability of the copolymers decreases with an increase in the mole fraction of MMA in the copolymers. Glass transition temperature of the copolymers was found to increase with an increase in the mole fraction of BCPA in the copolymers.

Evaluating the acute toxicity of binary and ternary mixtures of Cu, Zn, As and Se to Daphnia magna: a component-based approach using isobologram analyses and ternary diagrams.

An understanding of the monomer reactivity ratios is extremely useful for tailoring copolymers with desired compositions for a diversity of end-use applications. In situ ATR-FTIR was employed to monitor the initial formation of copolymers of ethylene and vinyl acetate (VAc) during polymerization in the “green” solvent supercritical carbon dioxide (scCO2). To obtain the copolymer composition, a calibration curve of the absorbance ratio 1737/2929 cm−1 versus vinyl acetate content of poly(ethylene-co-vinyl acetate) (PEVA) was established, covering the range of 5−98 wt %. The reactivity ratios for copolymerization of ethylene and VAc in scCO2 were determined using both the Kelen−Tudos and the nonlinear least-squares (NLLS) methods. Off-line 1H NMR analysis was also utilized for obtaining the copolymer composition, by which the determined reactivity ratios were compared with the ones obtained using in situ FTIR. The effect of reaction temperature and pressure on reactivity ratios was examined at 50 and 72 °C and at 13.8 and 27.6 MPa, with the lower temperature and higher pressure conditions increasing the reactivity ratios slightly. In situ FTIR was found to be able to accurately measure the reactivity ratios, and both the Kelen−Tudos and NNLS methods gave similar results. The obtained reactivity ratios will promote the application of the green solvent scCO2 in the production of the widely commercialized copolymer PEVA.

Problems in the current experimental determination of radical reactivity ratios (i.e., 's values') in free-radical copolymerization and the resulting limited physical meaning of these reactivity ratios are highlighted in the present work. It is exemplified that the radical reactivity ratios obtained via fitting of average propagation rate coefficients are very sensitive to small uncertainties in monomer reactivity ratios and homopropagation rate coefficients. Furthermore, the failure to select an appropriate modelling method, and to design experiments so as to satisfy its assumptions, may lead to incorrect parameter estimates. These problems result in large uncertainties in the measured values of the radical reactivity ratios, which in turn lead to large uncertainties in calculated ratios of propagating radical concentrations. This suggests that experimental determinations of the relative radical concentrations may lead to complimentary means for obtaining information on radical reactivity ratios, and possible ways of obtaining this information through catalytic chain transfer experiments are discussed.

Reactivity ratios in copolymerizations involving allyl methacrylate