Comonomer Feed Ratio Research Articles

Microstructure determination of acrylonitrile/butyl methacrylate copolymers using 13C NMR spectroscopy

AbstractAcrylonitrile/butyl methacrylate (A/B) copolymers were prepared in bulk with different comonomer feed ratios. The copolymer composition obtained from the total nitrogen content was used for calculating the reactivity ratios. Information about sequence distributions was obtained from 13C NMR spectroscopy. The relative amounts of A‐ and B‐centred triads were evaluated by using nitrile (CN) and carbonyl (CO) carbon resonances, respectively, and have been found to be in a good agreement with those expected theoretically.

Preparation of a thermally phase‐separating copolymer, poly(N‐isopropylacrylamide‐co‐N‐acryloxysuccinimide), with a controlled number of active esters per polymer chain

AbstractN‐isopropylacrylamide and N‐acryloxysuccinimide have been copolymerized in various mixtures of terrahydrofuran and toluene using azobisisobutyronitrile as initiator. Polymerization has been conducted for 24 h at 50°C under a slightly positive pressure of nitrogen. The copolymers were assayed for active ester content by measuring the UV absorbance (259 nm) of N‐hydroxysuccinimide anion, generated by reacting the copolymers with N‐isopropylamine in dimethylformamide and dissolving the resulting mixture in 0.1M HEPES buffer, pH 7.5. The molecular weight and its distribution have been estimated by gel permeation chromatography. The active ester content was found to be equivalent to the comonomer feed ratio, and the major factor controlling the molecular weight was the ratio of tetrahydrofuran to toluene. Thus, the number of active esters per polymer chain could be controlled by adjustment of the comonomer feed ratio and the ratio of tetrahydrofuran to toluene. Monomer reactivity ratios for copolymerization of N‐isopropylacrylamide with N‐acryloxysuccinimide were also estimated. These copolymers are useful for immobilizing binding ligands such as antibodies for subsequent thermally induced precipitation immunoassays and bioseparation processes.

New isomers of poly(vinyl fluoride) with controlled regiosequence microstructure

The addition polymer of vinyl fluoride, PVF, contains head-to-head and tail-to-tail structural irregularities (regiosequence defects) caused by monomer reversals during chain propagation. Previously no method existed for significantly altering the level of regiosequence defects, which typically amounts to 10% reverse addition and changes little with polymerization temperature. We report here a novel synthetic procedure which enables us to adjust this defect level by reductive dechlorination of precursor copolymers of vinyl fluoride, VF, with suitable chlorofluoroethylenes, using tributyltin hydride to replace chlorine quantitatively with hydrogen. The products are regioisomers of PVF with defect levels depending on the identity of the chlorofluoroethylene monomer, and the composition of the precursor copolymer, which is selected by adjusting the comonomer feed ratio. Reduction of VF copolymers with vinylidene chlorofluoride yields PVF with defect levels in the range 0–10%, whereas reduction of VF copolymers with 1-chloro-2-fluoroethylene yields PVF with 10–30% defects. We measure the regiosequence distribution of these various PVF isomers by 470 MHz 19F nuclear magnetic resonance, and show that the polymers are stereoirregular (atactic) as well. The crystalline melting temperature of PVF increases as the polymer becomes more isoregic.

The kinetics of solution copolymerization of vinyl chloroacetate with vinyl acetate in a CSTR

AbstractThe kinetics of isothermal, solution copolymerization of vinyl chloroacetate (VCLAC) with vinyl acetate (VAC) in methyl isobutyl ketone (MIBK) has been investigated using a continuous flow stirred‐tank reactor (CSTR). The initiator used was 2,2′‐azobis 2,4‐dimethyl valeronitrile (ADVN). Polymerizations were carried out to moderately high conversions, necessitating the use of a modified parameter estimation method to determine the reactivity ratios. The copolymer composition conforms to terminal model kinetics. The values obtained for r1 and r2 are 1.18 and 0.80, respectively, with VCLAC as M1 and VAC as M2. Both values are close to unity indicating random copolymerization. The cross termination factor ϕ strongly depends on the composition of the comonomer feed ratio, implying that the chain‐termination step is possibly diffusion controlled. The variation of ϕ could also be caused by chain transfer to the solvent retarding the reaction rate. Such a possibility is consistent with the observed reduction in the molecular weight of the copolymer in the presence of the solvent. The approach to steady‐state in the reactor was characterized. It was not possible to obtain good agreement between experiment and simulation with a single value of the ϕ factor.

Poly(alkylene oxide) ionomers. XI. Polymerization and copolymerization of methyl ω‐epoxyundecanoate and characterization of the polymers

AbstractMethyl 10‐undecenoate was epoxidized in nearly quantitative yield with m‐chloroperoxy‐benzoic acid to methyl 10,11‐epoxyundecanoate. The functional epoxide monomer was polymerized by the reaction product of triethylaluminum/water/acetylacetone (1.0/0.5/1.0) to a high molecular weight elastomer having pendent carboxyl groups, and a molecular weight distribution near the most probable distribution. With the same initiator system, methyl 10,11‐epoxyundecanoate was copolymerized with ethylene oxide, propylene oxide, 1‐butene oxide, 1‐hexene oxide, phenyl glycidyl ether, epichlorohydrin, and 4,4,4‐trichloro‐1‐butene oxide. The copolymers were typically high in molecular weight, elastomeric, and had methyl 10,11‐epoxyundecanoate incorporations similar to the initial feed ratio of comonomers. The new family of functional polymers were characterized by their infrared and NMR spectra, dilute solution viscosity and thermal transitions.

Poly(alkylene oxide) ionomers. X. Copolymerization of methyl ω‐epoxyalkanoates and characterization of the polymers

AbstractSelected methyl ω‐epoxyalkanoates ranging from methyl 3,4‐epoxybutanoate to methyl 7,8‐epoxyoctanoate were copolymerized with a number of oxiranes and with oxetane. Tetrahydrofuran did not take part in the attempted methyl ω‐epoxyalkanote–tetrahydrofuran copolymerization, but acted only as the solvent. The oxirane copolymers had polymer compositions similar to the comonomer feed ratio. Oxirane comonomers used were propylene oxide (1,2‐epoxypropane), butylene oxide (1,2‐epoxybutane), 1,2‐epoxyhexane, epichlorohydrin, and phenylglycidyl ether. The initiator system used was triethylaluminum/water/acetylacetone (1.0/0.5/1.0) in about 5 mol %. In the copolymerizations using methyl 3,4‐epoxybutanoate as a comonomer, only small yields of polymer (in the range of 1 to 2%) were realized, while for methyl 4,5‐epoxypentanoate the yields were generally in the range of 20 to 60%. Methyl 7,8‐epoxyoctanoate copolymerized readily and gave yields of copolymers of 50 to 90%.

Polymer conformation and NMR chemical shifts, 7. Conformational analysis of random copolymers

AbstractA method is developed for the conformational analysis of copolymers with randomly distributed stereo‐ and comonomer‐sequences. The conformational probabilities of dyad sequences constituting a random copolymer chain are calculated as a function of the copolymer composition which is derived from the monomer reactivity ratios and the comonomer feed ratio. The applicability of this method is verified in the conformational analyses of poly(methyl acrylate‐co‐styrene) and poly(methyl methacrylate‐co‐styrene). The calculation indicates that the conformational stabilities of dyad sequences are scarcely dependent on the copolymer composition in the former copolymer, whereas they are susceptible to the composition in the latter copolymer. This conformational behavior apparently reflects the geometrical difference between the copolymers: the former is composed of two mono‐substituted monomers and the latter of sterically nonequivalent monomers, viz. mono‐ and di‐substituted vinyl compounds. The composition‐dependences of 13C NMR chemical shifts of these copolymers are interpreted, based on the conformational calculation by this method.

Kinetic Features and Mechanism of Alternating Copolymerization of lndene with Maleic Anhydride

Abstract The radical copolymerization of indene (IN) with maleic anhydride (MA) was investigated. The charge-transfer complexes (CT complexes) between comonomers were studied by means of spectrophotometric measurements. It was found that the maximum copolymerization rate occurred at a comonomer feed ratio that did not correspond to the composition of the CT complex and the composition of copolymer. It was shown that rate maximum was displaced towards an excess of IN in the solvents with strong donicity. The Acceptor Number of solvent influences neither the initial rate nor the position of the rate maximum. Some kinetic calculations were made to assess values of the cross-propagation rate constants and to elucidate the mechanism of propagation of macromolecular chains.

Functional monomers and polymers. XIX. Copolymerization of vinyl monomers containing nucleic acid bases

AbstractTaking into account the specific base–base interaction existing between nucleic acid molecules, we studied the free‐radical copolymerization of N‐β‐methacryloyloxyethyl derivative of uracil with that of adenine at 60°C in various solvents. N‐β‐Methacryloyloxyethyltheophylline as well as methyl methacrylate were used also as comonomers. From the data on the rates in different comonomer feed ratios and the r1 and r2 values obtained, copolymerizability was discussed in some detail. The results suggest that the interaction between uracil and adenine bases plays a role in the copolymerization behavior.

Copolymerization of Dienophiles and Bicyclic Dienes

Abstract Copolymers of 5-methylenebicyclo(2.2.1)-2-heptene and maleic anhydride were prepared by free radical copolymerization. Copolymers of constant composition with an alternating arrangement of comonomers but of varying solubilities, degrees of cross-linking, and molecular weights were obtained. The effects of comonomer feed ratios, comonomer concentration, initiator concentration, and temperature were studied. Copolymers of 5-methylenebicyclo(2.2.1)-2-heptene and maleimide, bicyclo(2.2.1)-2,5-heptadiene and maleic anhydride, and 1,2,3,4,4a,5,8,8a-octahydro-2-methylene-l,4,5,8dimethanonaphthalene and maleic anhydride were also investigated.