Polyester Macromonomer Syntheses and Radical Copolymerization Kinetics with Styrene

Abstract

Short-chain polyester methacrylate macromonomers with alkyl, tertiary amine, carboxyl, and hydroxyl end-group functionalities are synthesized by ring-opening polymerization and subsequent modification. Monomer conversion and composition drift during batch radical copolymerizations of (macro)­monomer with styrene are tracked using the in situ NMR technique in both polar and nonpolar deuterated solvents at 80 °C. For experiments with initial methacrylate molar fraction f xMA = 0.2, the effects of end-group functionality, solvent, and hydrogen bonding on relative reactivity are pronounced for monomeric analogues of the macromonomers. However, the polyester spacers significantly dilute these effects in macromonomer copolymerization, as polyester type, length, and end-group functionality did not influence copolymerization kinetics. Instead, the chemical identity up to several units from the methacryloyl group is the most important indicator of macromonomer relative reactivity.

Polylactic acid macromonomer radical propagation kinetics and degradation behaviour

“…In other words, the presence of polar or steric groups further along the ester side chain does not decisively impact the bulk kp of PLANEMA systems. In support of this claim, we found that polyester type, length, and end-group functionality did not contribute to the relative reactivity of various methacrylate macromonomers and ST copolymerization systems, 28 and other work showed that the influence of the N,N-dimethylamino substituent on bulk kp is diluted from DMAEMA to DMAPMAE. 48 Furthermore, while Siegmann et al measured a 50% increase in bulk kp for PEGEEMA (3 PEG units) compared to EEMA (1 PEG unit) at 25 °C, 33 Smolne et al found no further increase in the bulk kp of PEGMA (7-8 PEG units) compared to that reported for PEGEEMA.…”

“…All (macro)monomer and poly(macromonomer) 1 H NMR characterizations were performed on a Bruker Avance instrument operating at 400 MHz using the peak assignments and calculations presented in our previous copolymerization study. 28 Alkyl Terminated Monomer: The synthesis of PLA1EMA was performed as previously reported, 28 with the exception that EtOAc was used as the methacrylation solvent instead of THF.…”

“…The syntheses of PLANEMA macromonomers were conducted as previously reported for N = 5, 28 except with EtOAc used as the methacrylation solvent instead of THF; synthesis characterization for N = 7 and N = 9 is detailed by Table S1 and SEC oligomeric molar mass distributions are shown in Figure S1. LA (5.27 g, 36.6 mmol) was loaded into a 50 mL sealed round bottom flask, purged with nitrogen, and then heated to 130 °C.…”

“…It should be noted that although HEMA-PLA5 and PLA5EMA have similar average MW, the former are predominantly even numbered oligomers (i.e., 2n = 2, 4, 6) while the latter are predominantly odd numbered oligomers (i.e., N = 3, 5, 7) because the ETL initiator fragment contributes a single PLA unit to each polyester chain. 28 4 | J. Name., 2012, 00, 1-3…”

“…Although studied under limited conditions, typical methacrylate/methacrylate relative reactivity -i.e., equal addition probabilities -was demonstrated for HEMA-PLA2n and polycaprolactone (PCL) based HEMA-PCLn macromonomer copolymerizations with methyl methacrylate (MMA), [25][26][27] while another study detailing the copolymerization of styrene (ST) with polyester methacrylate type macromonomers showed that the relative reactivity depends only on the chemical identity up to several units away from the methacryloyl endgroup. 28 In terms of propagation rate behaviour, the pulsed laser polymerization coupled with size exclusion chromatography (PLP-SEC) technique is the most accurate and reliable method for determining propagation rate coefficients (kp), as is described in comprehensive detail by Beuermann and Buback. 29 The kp is calculated according to Eqn.…”