Monomer Distribution In Copolymers Research Articles

Conventional Oxyanionic versus Monomer-Activated Anionic Copolymerization of Ethylene Oxide with Glycidyl Ethers: Striking Differences in Reactivity Ratios.

Detailed understanding of the monomer distribution in copolymers is essential to tailor their properties. For the first time, we have been able to utilize in situ 1H NMR spectroscopy to monitor the monomer-activated anionic ring opening copolymerization (AROP) of ethylene oxide (EO) with a glycidyl ether comonomer, namely, ethoxy ethyl glycidyl ether (EEGE). We determine reactivity ratios and draw a direct comparison to conventional oxyanionic ROP. Surprisingly, the respective monomer reactivities differ strongly between the different types of AROP. Under conventional oxyanionic conditions similar monomer reactivities of EO and EEGE are observed, leading to random structures (rEO = 1.05 ± 0.02, rEEGE = 0.94 ± 0.02). Addition of a cation complexing agent (18-crown-6) showed no influence on the relative reactivity of EO and EEGE (rEO = rEEGE = 1.00 ± 0.02). In striking contrast, monomer-activated AROP produces very different monomer reactivities, affording strongly tapered copolymer structures (rEO = 8.00 ± 0.16, rEEGE = 0.125 ± 0.003). These results highlight the importance of understanding reactivity ratios of comonomer pairs under certain polymerization conditions, at the same time demonstrating the ability to generate both random and strongly tapered P(EO-co-EEGE) polyethers by simple one-pot statistical anionic copolymerization. These observations may be generally valid for the copolymerization of EO and glycidyl ethers.

Block microstructural characterization of copolymers formed from fluorinated and non-fluorinated alkyl polyisocyanates using desorption chemical ionization mass spectrometry

Homopolymers and copolymers of 1-isocyanato-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononane (monomer F) and n-hexylisocyanate (monomer H) were examined by desorption chemical ionization mass spectrometry (DCI-MS) to obtain information on the monomer distribution in the copolymers. Tandem mass spectrometry (MS/MS) was used to characterize ions generated by DCI in the mass spectrometer ion source; ammonia and isobutane were selected as chemical ionization (CI) reagent gases. The major peaks in the ammonia DCI mass spectrum of poly(4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononyl)isocyanate (poly ( F)) are protonated and ammoniated trimers. This result suggests that on pyrolytic degradation poly ( F) forms cyclic trimers as do alkyl isocyanate polymers. The isobutane DCI mass spectra display the characteristic alkene elimination sequence characteristic of poly( n-hexyl)isocyanate and poly(2,6-dimethylheptyl)isocyanate but with additional extensive fragmentation. The major fragment ion is the protonated monomer. The monomer distributions in copolymers comprised of monomer F and monomer H were deduced from the abundances of various protonated and ammoniated trimers in the ammonia DCI mass spectra using Markovian statistics. Both soluble and insoluble copolymer samples were isolated and found to have non-random monomer distributions. The soluble fraction is dominated by monomer H blocks while the insoluble fraction also contains a majority of monomer H blocks but relatively more monomer F blocks. This forms an example in the polyisocyanates, which hitherto exhibited only random copolymerization, of a non-living method of polymerization yielding a block microstructure for a mixture of two monomers with virtually identical polymerizable functions. Mass spectrometry offers information on chain microstructure which would be unavailable by other means.

Copolymerization of 4-methylpentene-1 and styrene with TiCl 3 and iBu 3Al and the copolymer structure

Copolymers of 4-methylpentene-1 and styrene were prepared (TiCl 3-AliBu 3, 70°) and their structure investigated. Monomer reactivity ratios calculated from the copolymer compositions were found to be 3·92 and 0·98. Comparison of the i.r. spectra of copolymers thus prepared and of isotactic homopolymers (poly-4-methylpentene-1 and polystyrene) allowed some estimation of monomer distribution in copolymers of different composition; this estimation for styrene units was based on band intensities at 565, 1084 and 985 cm −1, and for 4-methylpentene-1 units on band intensity at 997 cm −1. These data show the copolymers of 4-methylpentene-1 and styrene to have random structure, and to be described by statistic relationships corresponding to r 1r 2 ≈ 1. Possible reasons for discrepancies between r 1r 2-values from compositional studies and those obtained from i.r. data are discussed.

Non-Markoffian Monomer Distributions in Copolymers. The Copolymerization of Ethylene Oxide and Maleic Anhydride

Non-Markoffian Monomer Distributions in Copolymers. The Copolymerization of Ethylene Oxide and Maleic Anhydride

Catalyst-Controlled Monomer Distributions in Copolymers. Copolymerization of Propylene Oxide and Maleic Anhydride

Catalyst-Controlled Monomer Distributions in Copolymers. Copolymerization of Propylene Oxide and Maleic Anhydride

Random Monomer Distributions in Copolymers. Copolymerizations of Ethylene-Vinyl Chloride and Ethylene-Vinyl Acetate

Random Monomer Distributions in Copolymers. Copolymerizations of Ethylene-Vinyl Chloride and Ethylene-Vinyl Acetate

Formation of random copolymers

AbstractAssumptions in the derivation of the copolymerization equation, experimental errors in its application, and recent developments in quantitative correlations of reactivity data in free radical polymerizations are considered. Fewer monomers are susceptible to cationic or anionic polymerizations and differences in reactivity among these monomers are so large that practical possibilities of making copolymers by ionic reactions are limited. Numerous experimental variables complicate assembly and correlation of experimental data on ionic copolymerizations and the present status of such efforts is summarized. Similar considerations apply also, often to a greater degree, to copolymerizations by transition metal and metal oxide catalysts. Some simple expressions for monomer distributions in copolymers are given.