Group-Transfer Polymerization of Various Crotonates Using Organic Acid Catalysts

Copolymers incorporated with β-substituted acrylate synthesized by organo-catalyzed group-transfer polymerization

Various copolymers incorporated with β-substituted acrylates, such as alkyl crotonates (e.g., methyl crotonate (MC), ethyl crotonate (EC), isopropyl crotonate (iPC), and n-butyl crotonate (nBC)) and methyl cinnamate (MCin), were synthesized by group-transfer polymerization (GTP) using a silicon-based Lewis acid catalyst. In addition to β-substituted acrylates, α-substituted acrylates (e.g., methyl methacrylate (MMA) and n-butyl methacrylate (nBMA)) were examined as comonomers. Proton nuclear magnetic resonance (1H NMR) spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) characterizations of the obtained copolymers revealed that each monomer component was incorporated sufficiently. The thermal stabilities of the resulting copolymers were investigated by dynamic mechanical analysis (DMA), indicating that the glass-transition temperature (Tg) of the copolymers can be widely varied over a relatively high-temperature range by selecting the optimal comonomer. More specifically, the Tg values of poly(MC-random-EC) (MC/EC molar ratio = 50/50), poly(MC-random-nBC) (MC/nBC molar ratio = 50/50), poly(MC-random-MCin) (MC/MCin molar ratio = 54/46), and poly(nBC-random-MCin) (nBC/MCin molar ratio = 56/44) were 173, 130, 216, and 167 °C, respectively.

Compounded Sequence Control in Polymerization of One-Pot Mixtures of Highly Reactive Acrylates by Differentiating Lewis Pairs

The ability to synthesize well-defined block copolymers (BCPs) from one-pot comonomer mixtures has powerful chemical and practical implications. However, controlling sequences between highly reactive, homologous comonomers such as acrylates during polymerization is challenging. Here we present a Lewis pair polymerization strategy that uniquely utilizes preferential Lewis acid coordination to differentiate between comonomers, distinctive kinetics, and compounded thermodynamic and kinetic differentiation to precisely control sequences and suppress tapering and misincorporation errors, thus achieving well-defined and resolved di- or tri-BCPs of acrylates.

Kinetic modeling study of the group-transfer polymerization of alkyl crotonates using a silicon Lewis acid catalyst

Kinetic modeling is effective in the development of efficient and manageable polymerization systems.

Unique acrylic resins with aromatic side chains by homopolymerization of cinnamic monomers

Cinnamic monomers, which are useful chemicals derived from biomass, contain α,β-unsaturated carbonyl groups with an aromatic ring at the β-position. Homopolymers synthesized by addition polymerization of these compounds are expected to be innovative bio-based polymer materials, as they have both polystyrene and polyacrylate structures. However, polymerization of these compounds by many methods is challenging, including by radical methods, owing to steric hindrance of the substituents and delocalization of electrons throughout the molecule via unsaturated π-bonding. Herein we report that homopolymers of these compounds with molecular weights (Mn) of ~18,100 g mol−1 and controlled polymer backbones can be synthesized by the group-transfer polymerization technique using organic acid catalysts. Additionally, these homopolymers are shown to have high heat resistance comparable to that of engineering plastics. Overall, these findings may open up possibilities for the convenient homopolymerization of cinnamic monomers to produce high-performance polymer materials.