Preparation and Analysis of Cross-Linking Copolymers

Abstract

Copolymerization of ST (styrene) with EDM (ethylene glycol dimethacrylate) gives nonlinear polymers. The average molecular weight and polydispersity of copolymers composed of ST and EDM were measured using the GPC (gel permeation chromatography) technique, and an exponential increase in both quantities with reaction time was observed. 1 H and 13 C NMR spectra of the copolymers were taken to prove the structure and purity of the products and to calculate the composition and pendant content of the copolymers. The ratio of the pendant double bonds of the copolymers was determined from the 1 H NMR spectra. A remarkable increase in the ratio of the pendant double bonds with reaction time was observed. The mechanism for the chain propagation was studied and found to follow the terminal model. Reacitvity ratios were found to be r1 ) 0.452 ( 0.031 for monomer ST and r2 ) 0.297 ( 0.027 for monomer EDM. According to the size distribution of the copolymers measured by DLS (dynamic light scattering) and the average radii of gyration measured by SLS (static light scattering) techniques, the samples showed strong polydispersity and an increase in molecular size with reaction time. Unusually high molecular weight values were observed after a certain reaction time.

Extent of intramolecular cyclization in RAFT-synthesized methacrylic branched copolymers using 13C NMR spectroscopy

“…13 C NMR spectra of the branched copolymers were analyzed using Topspin 2.1.6 software (Bruker Biospin). The relatively broad and complex 13 C NMR signals corresponding to the two oxymethylene carbons (-O-CH 2 -CH 2 -S-S-: 62.42 ppm) due to the fully reacted DSDMA residues were deconvoluted using a Lorentzian fit.…”

“…36,37 Nevertheless, in their analysis of crosslinked copolymers, Borbély et al 13 stated that the oxymethylene signals of copolymerized ethylene glycol dimethacrylate units appear at 60-64 ppm. Table 1 Summary of branched copolymer compositions (*targeted composition, **calculated by end-group 1 H NMR analysis; soluble fraction), and final comonomer conversions for a series of soluble branched copolymers prepared by RAFT copolymerization of MMA with DSDMA at various initial comonomer concentrations using increasing amounts of DSDMA branching comonomer.…”

“…Over the past few decades, 13 C NMR spectroscopy has been demonstrated to be a versatile characterization tool in polymer science. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] For example, the extent of long-chain branching has been assessed during the free radical solution polymerization of n-butyl acrylate, vinyl acetate or 2-ethylhexyl acrylate.…”

Viscoelastic Relaxation of Cross-Linked, Alternating Copolymers in the Free-Draining Limit

“…[29][30][31] The second type of networks are those attained through chemical reactions, leading to the formation of permanent cross-links, [32][33][34] such as the copolymerization of styrene with ethylene glycol dimethacrylate. 35 In this work, we focus on the case of permanent crosslinks. In fact, the proposed approach can also be applied to transient networks (gels) as long as one measures on time scales smaller than the average lifetime of the cross-links in the gel.…”

Solvent effects on the kinetics of gelation and the crosslink density of polysiloxane gels

“…The real time absorbance of the samples was measured, compared and evaluated for gel point times and kinetic parameters of gelation by FTIR [30]. The conversion of the main gelator could also be estimated and related to the gel point, following the pre-gel and the post-gel reactions [31,32].…”