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

Abstract

Bio-based platform molecules such as itaconic, fumaric, and muconic acid offer much promise in the formation of sustainable unsaturated polyester resins upon reaction with suitable diols and polyols. The C=C bonds present in these polyester chains allows for post-polymerization modification and such moieties are conventionally utilized in curing processes during the manufacture of coatings. The C=C modification sites can also act as points to add useful pendants which can alter the polymers final properties such as glass transition temperature, biodegradability, hardness, polarity, and strength. A commonly observed modification is the addition of secondary amines via an aza-Michael addition. Conventional procedures for the addition of amines onto itaconate polyesters require reaction times of several days as a result of undesired side reactions, in particular, the formation of the less reactive mesaconate regioisomer. The slow reversion of the mesaconate back to itaconate, followed by subsequent amine addition, is the primary reason for such extended reaction times. Herein we report our efforts toward finding a suitable catalyst for the aza-Michael addition of diethylamine onto a model substrate, dimethyl itaconate, with the aim of being able to add amine onto the itaconate units without excessive regioisomerization to the inactive mesaconate. A catalyst screen showed that iodine on acidic alumina results in an effective, heterogeneous, reusable catalyst for the investigated aza-Michael addition. Extending the study further, itaconate polyester was prepared by Candida Antartica Lipase B (CaL-B) via enzymatic polytranesterification and subsequently modified with diethylamine using the iodine on acidic alumina catalyst, dramatically reducing the required length of reaction (>70% addition after 4 h). The approach represents a multidisciplinary example whereby biocatalytic polymerization is combined with chemocatalytic modification of the resultant polyester for the formation of useful bio-based polyesters.

Effect of 1,2,4,5-Benzenetetracarboxylic Acid on Unsaturated Poly(butylene adipate-co-butylene itaconate) Copolyesters: Synthesis, Non-Isothermal Crystallization Kinetics, Thermal and Mechanical Properties

“…Unsaturated aliphatic polyester has been amended to practice the partial cross-linking via UV curing processing to adjust their physical property or through the cross-linking process with covalent bonds to produce thermoset-like copolyesters [9][10][11][12], or by combining it with epoxy materials [13][14][15]. The purpose of this operation is to achieve tremendous physical-chemical properties that provide unique characteristics of copolyesters, such as stronger hardness, higher rigidity, better tensile strength, chemical resistance and thermal stability [16][17][18].…”

Toward Renewable and Functional Biomedical Polymers with Tunable Degradation Rates Based on Itaconic Acid and 1,8-Octanediol

“…59 The Ordelt saturation and isomerization side reactions highlighted here not only limit the bioreactivity of ITA but could also lead to the excess of OD in polymer compositions when calculated from NMR analyses. 43 The Ordelt saturation side reaction can also occur to a greater extent in acidic environments. 39 The choice of the catalyst can limit the extent of such side reactions; Pellis et al demonstrated that compared to traditional catalysts, the use of enzyme-catalyzed polymerization is an effective means of preserving the ITA structure and avoiding isomerization or Ordelt saturation.…”

“…First, to estimate the integrated monomer content (OD and ITA) in the polyester, the peak integration values of the respective backbone 1 H NMR peaks for ITA (peak b , expected two protons/molecule) and OD (peak e , expected 8 protons/molecule) were compared to the polyester identified in spectral assessment (eqs and ). The portions of ITA within the polymer backbone that are impacted by isomerization and oxo-Michael addition were also included in the equation, represented by integration of peak i (expected 1 proton/molecule) ,, and peak j (expected 1 proton/molecule), respectively. …”

Achievements and Trends in Biocatalytic Synthesis of Specialty Polymers from Biomass-Derived Monomers Using Lipases

“…Enzymatic synthesis of itaconate co-polymers and terpolymers with several diols and diacids or diesters emerged as one of the best possibilities to preserve the itaconate double bound, avoiding the undesirable side reactions which are common during the conventional polyesterification of such monomers [184]. In this way, the post-polymerization modification of these polymers, e.g., by aza-Michael additions, becomes more effective, particularly when itaconate is present as a terminal unit.…”