Insights into post‐polymerisation modification of bio‐based unsaturated itaconate and fumarate polyesters via aza‐michael addition: Understanding the effects of CC isomerisation

Abstract

Development of renewable bio‐based unsaturated polyesters is undergoing a renaissance, typified by the use of itaconate and fumarate monomers. The electron‐deficient C=C bond found on the corresponding polyesters allows convenient post‐polymerisation modification to give a wide range of polymer properties; this is notably effective for the addition of nucleophilic pendants. However, preservation of unsaturated functionality is blighted by two undesirable side‐reactions, branching/crosslinking and C=C isomerisation. Herein, a tentative kinetic study of diethylamine addition to model itaconate and fumarate diesters highlights the significance of undesirable C=C isomerisation. In particular, it shows that reversible isomerisation from itaconate to mesaconate (a poor Michael acceptor) is in direct competition with aza‐Michael addition, where the amine Michael donor acts as an isomerisation catalyst. We postulate that undesired formation of mesaconate is responsible for the long reaction times previously reported for itaconate polyester post‐polymerisation modification. This study illustrates the pressing need to overcome this issue of C=C isomerisation to enhance post‐polymerisation modification of bio‐based unsaturated polyesters. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1935–1945

First Example of Unsaturated Poly(Ester Amide)s Derived From Itaconic Acid and Their Application as Bio-Based UV-Curing Polymers

“…These have been used as reactive binder resins for coatings, shape-memory materials, printing inks, etc [21][22][23][24][25]. In addition, these polyesters have been exploited in post-polymerization modification reactions to obtain new polymeric structures [26][27][28][29]. However, to date, no examples of unsaturated poly(ester amide)s based on itaconic acid have been reported.…”

Elastomeric polyamide biomaterials with stereochemically tuneable mechanical properties and shape memory

“…Nonetheless, polyesters or poly(ester-amide)s [22][23][24] , prepared with pre-defined stereochemical units, such as fumaric acid, have garnered attention as biomaterials [25][26][27][28][29][30][31][32][33][34] . However, maleate-based materials have been notoriously hard to prepare due to isomerization issues 35,36 and, with the exception of a recent report 37 , only low-molecular-weight polymers have been isolated 38,39 , which reduces the durability of the materials. Furthermore, stereochemistry has not been directly invoked in order to modulate properties in most of these examples.…”

Improving the Post-polymerization Modification of Bio-Based Itaconate Unsaturated Polyesters: Catalyzing Aza-Michael Additions With Reusable Iodine on Acidic Alumina

“…In alignment with our previous study into the un-catalyzed addition of amines on polyesters (Farmer et al, 2018b; Pellis et al, 2019), we first elected to study the room temperature addition of DEA using DMI as a model compound (Figure 4) representing the UPRs constitutional repeat unit (CRU). Use of a small model compound also aided analysis and avoided issues of changing reaction viscosity and consequently, effects of mass transfer.…”

“…Chanda reported 3 day long additions of both thiols and amines to poly(dodecyl itaconate) UPEs (Chanda and Ramakrishnan, 2015), while Winkler published thio-Michael additions that ran overnight using a 5-times molar excess of donor, and requiring 10 mol% hexylamine as a catalyst (Winkler et al, 2015). In a recent study it was shown that during aza-Michael addition of diethyl amine (DEA) onto dimethyl itaconate (DMI, a mimic for the itaconate unit in polyesters) regioisomerization (k 2 ) is in direct competition with desired addition (k 1 ) (Figure 4; Farmer et al, 2018b). Mesaconate (DMMes) formation was proven to be catalyzed by the amine Michael donor (DEA) but because the DMMes itself does not act as an acceptor (compounds 2 or 3 were not detected, Figure 4) the lengthy reaction times were deemed to be necessary.…”