Zwitterion polymerization of 2-methyl-2-oxazoline and acrylic acid

Abstract

The zwitterion polymerization of 2-methyl-2-oxazoline (MeOXO) and acrylic acid (AA) has been investigated in bulk and solution (DMF and acetonitrile) at 60-70 °C. Vapor pressure osmometry showed the number-average molecular weight to be in the range 590-2760, depending on reaction conditions. The copolymer composition was established as 1:1 (MeOXO:AA) by proton NMR. Proton and 13C NMR spectroscopy identified the repeating unit as -CH2CH2N(COCHg)CH2CH2COO-and the end groups as olefinic, carboxyl, and acetamido. Infrared spectroscopy supports the NMR results. Hydrolysis experiments corroborated both the copolymer composition and identity of end groups. High-performance liquid chromatography showed that the copolymer product consists of different-sized molecules and not all molecules have the same two end groups. A mechanism is proposed to describe the MeOXO-AA polymerization. MeOXO and AA form a genetic zwitterion which is responsible for initiation. Polymer growth involves various-sized zwitterions reacting with each other and with the genetic zwitterion by a ring-opening attack of carboxylate anion on the quaternary MeOXO ring. Termination occurs by reaction of growing zwitterions both with acrylic acid and with a quaternized MeOXO-acrylate salt (formed by proton transfer between MeOXO and AA). Direct proton NMR analysis of the polymerizing MeOXO-AA system gave evidence for the genetic zwitterion. 70 55 1850 B (soln6) 70 60 2000 B (bulk) 70 69 1960 B (bulk) 100 21 590 C (bulk) 70 41 2760 0 p-Methoxyphenol present in all experiments.6 Solution polymerization in CH3CN.c Solution polymerization in DMF. 8 Yield for recrystallized polymer.

Chain and Step Growth Polymerizations of Cyclic Imino Ethers: From Poly(2‐oxazoline)s to Poly(ester amide)s

“…[17a] CIE have been shown to be powerful M N reacting with M E including acrylic acid, acrylamide, propiolactone, anhydrides and sulfolactones (Table ). Unsaturated and saturated carboxylic acids and their derivatives have attracted significant attention as functional M E s as they provide access to degradable poly(ester amide)s with the amide functionality in the side chain, also referred to N‐ acylated poly(aminoester)s (NPAEs). However, the degradability of the polymers have only been tested by alkaline hydrolysis (sodium hydroxide, 100 °C, 3 h) so far .…”

Catalytic conversion of glycerol to polymers in the presence of ammonia

“…The peaks at 176 and 178 ppm have been attributed to the presence of the C=O functional group in the polymeric mixture. Peaks in the range of 63 -68 ppm were assigned to the methylene carbon in -CH 2 OC=O, which suggests then presence of ester linkages [13,17]. These assignments were confirmed by chemical tests: while the same solution analysed by NMR tested negative to the 2,4dinitrophenylhydrazine (DNPH) test (where a yellow/orange precipitate was absent), a positive result was obtained for the hydroxamic acid test suggesting that the carbonyl group observed on the 13 C NMR spectrum is not from a ketone nor an aldehyde but from an ester and/or amide.…”

“…For instance, polyamides have been previously obtained from amines and carboxylic acids using 3,4,5-trifluorophenylboronic acid as catalyst [12]. Oxazolines have been reported to spontaneously polymerise with α,β-unsaturated acids through a ring opening mechanism via a zwitterion [13]. Likewise, the spontaneous polymerisation of acrylamide has been claimed to occur in glycerol solution [14].…”

Ring‐Opening Polymerization

“…With only a very few exceptions, these polymerizations do not yield polymer molecular weights higher than 1000-3000. Low molecular weights are a consequence of the low concentration of the reacting species, the zwitterions, coupled with facile termination of the zwitterion þ and À centers by reaction with the nucleophilic and electrophilic monomers [Odian and Gunatillake, 1984;Odian et al, 1990]. High molecular weights are obtained in zwitterion polymerizations only when the zwitterion concentrations are high relative to other materials present that can act as terminating agents.…”