Recent advances in the synthesis of biodegradable polyesters by sustainable polymerization: lipase-catalyzed polymerization

Over the past three decades, enzymatic polymerization has dramatically developed and gradually broadened as a creative methodology in the construction of polymeric materials with tailor-made structures and properties. Compared with transition metal catalyst polymerizations, enzymatic polymerization is more attractive in the biomedicine field due to the metal-free residue, good biocompatibility, and few by-products. Meanwhile, enzymatic polymerization has far more activity towards macrolides. In this review, the synthesis of lipase-catalyzed polymer materials is systematically summarized, focusing on the synthesis of the complex and well-defined polymers. The enzymatic polyester synthesis was then discussed concerning the different reaction types, including ring-opening polymerization, polycondensation, a combination of ring-opening polymerization with polycondensation, and chemoenzymatic polymerization. Besides, exploration of novel biocatalysts and reaction media was also described, with particular emphasis on the enzymes obtained via immobilization or protein engineering strategies, green solvents, and reactors. Finally, recent developments in catalytic kinetics and mechanistic studies through the use of spectroscopy, mathematics, and computer techniques have been introduced. Besides, we addressed the remaining central issues in enzymatic polymerization and discussed current studies aimed at providing answers.

Macromolecular Engineering by Applying Concurrent Reactions with ATRP

Modern polymeric material design often involves precise tailoring of molecular/supramolecular structures which is also called macromolecular engineering. The available tools for molecular structure tailoring are controlled/living polymerization methods, click chemistry, supramolecular polymerization, self-assembly, among others. When polymeric materials with complex molecular architectures are targeted, it usually takes several steps of reactions to obtain the aimed product. Concurrent polymerization methods, i.e., two or more reaction mechanisms, steps, or procedures take place simultaneously instead of sequentially, can significantly reduce the complexity of the reaction procedure or provide special molecular architectures that would be otherwise very difficult to synthesize. Atom transfer radical polymerization, ATRP, has been widely applied in concurrent polymerization reactions and resulted in improved efficiency in macromolecular engineering. This perspective summarizes reported studies employing concurrent polymerization methods with ATRP as one of the reaction components and highlights future research directions in this area.

Synthesis of lipase–polymer conjugates by Cu(0)-mediated reversible deactivation radical polymerization: polymerization vs. degradation

Cu(0)-RDRP was first used for the polymerization-induced self-assembly of lipase–polymer conjugates, inducing the formation of nanospheres with preserved activity and degradability.

Photocatalysis in organic and polymer synthesis

This review, with over 600 references, summarizes the recent applications of photoredox catalysis for organic transformation and polymer synthesis. Photoredox catalysts are metallo- or organo-compounds capable of absorbing visible light, resulting in an excited state species. This excited state species can donate or accept an electron from other substrates to mediate redox reactions at ambient temperature with high atom efficiency. These catalysts have been successfully implemented for the discovery of novel organic reactions and synthesis of added-value chemicals with an excellent control of selectivity and stereo-regularity. More recently, such catalysts have been implemented by polymer chemists to post-modify polymers in high yields, as well as to effectively catalyze reversible deactivation radical polymerizations and living polymerizations. These catalysts create new approaches for advanced organic transformation and polymer synthesis. The objective of this review is to give an overview of this emerging field to organic and polymer chemists as well as materials scientists.

From sequential chemoenzymatic synthesis to integrated hybrid catalysis: taking the best of both worlds to open up the scope of possibilities for a sustainable future

Here an overview of all pathways that integrate chemical and biological catalysis is presented. We emphasize the factors to be considered in order to understand catalytic synergy.

One-Pot Synthesis of Block Copolymers by Orthogonal Ring-Opening Polymerization and PET-RAFT Polymerization at Ambient Temperature

Well-defined poly(ε-caprolactone)-b-poly(methyl acrylate) (PCL-b-PMA) block copolymers were synthesized at ambient temperature by one-pot combination of diphenyl phosphate (DPP)-catalyzed ring-opening polymerization (ROP) and photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. Full orthogonality of PET-RAFT polymerization and DPP-catalyzed ROP was confirmed by kinetic studies, which allowed facile synthesis of PCL-b-PMA block copolymers without a specific polymerization sequence. The resulting PCL-b-PMA block copolymers synthesized by either sequential or simultaneous ROP and PET-RAFT polymerization showed remarkably low molecular weight distributions (≤1.15), indicating that both ROP and PET-RAFT polymerizations proceeded in a controlled manner. In contrast to previous synthetic methods to prepare block copolymers, this facile one-pot method allows for rapid synthesis of block copolymers controlled via visible light.

Facile synthesis of a multifunctional copolymer via a concurrent RAFT-enzymatic system for theranostic applications

Through a straightforward concurrent RAFT-enzymatic multicomponent polymerization system and subsequent post-polymerization modifications, a multi-functional copolymer for theranostic application has been efficiently prepared.

Fluorescent protein-reactive polymers via one-pot combination of the Ugi reaction and RAFT polymerization

Well-defined polymers containing both fluorescent and protein-reactive groups at the chain end have been facilely synthesized by the one-pot combination of the four-component Ugi reaction and RAFT polymerization.

Multicomponent Polymerization System Combining Hantzsch Reaction and Reversible Addition-Fragmentation Chain Transfer to Efficiently Synthesize Well-Defined Poly(1,4-dihydropyridine)s

A novel multicomponent system has been constructed through the combination of Hantzsch reaction and reversible addition-fragmentation chain transfer (RAFT) polymerization in a one-pot manner. Compared to traditional stepwise methods, this one-pot system exhibits much more advantages to facilely and efficiently prepare well-defined poly(1,4-dihydropyridine)s (poly(1,4-DHP)s). A series of poly(1,4-DHP) derivatives have also been successfully prepared through this Hantzsch-RAFT system using different aldehydes as reactants, suggesting this system is a general and versatile approach to prepare well-defined functional polymers with 1,4-DHPs as side groups. Since 1,4-DHP derivatives are an important class of bioactive molecules in the pharmaceutical field, this simple method to prepare poly(1,4-DHP)s might have potential to prepare related functional polymers for biological and pharmaceutical applications.

The power of one-pot: a hexa-component system containing π–π stacking, Ugi reaction and RAFT polymerization for simple polymer conjugation on carbon nanotubes

Ugi reaction has been recognized as a multicomponent click reaction to construct a hexa-component one-pot system with π–π stacking and RAFT polymerization for the simple (co)polymer modification of CNT surfaces.

Combining Enzymatic Monomer Transformation with Photoinduced Electron Transfer - Reversible Addition-Fragmentation Chain Transfer for the Synthesis of Complex Multiblock Copolymers

A novel and facile method, involving enzymatic monomer synthesis and a photocontrolled polymerization technique, has been successfully employed for the preparation of high-order multiblock copolymers. New acrylate monomers were synthesized via enzymatic transacylation between an activated monomer, i.e., 2,2,2-trifluoroethyl acrylate (TFEA), and various functional alcohols. These synthesized monomers were successfully polymerized without further purification via photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization under low energy blue LED light (4.8 W) in the presence of an iridium-based photoredox catalyst (fac-[Ir(ppy)₃]). In this condition, PET-RAFT allows us to achieve high monomer conversion (∼100%) with excellent integrity of the end group (>80%). Different multiblock (co)polymers, including poly(hexyl acrylate) pentablock homopolymer, poly(methyl acylate-b-ethyl acrylate-b-n-propyl acrylate-b-n-butyl acrylate-b-n-pentyl acrylate) pentablock copolymer, and poly(3-oxobutyl acrylate-b-methyl acrylate-b-3-(trimethylsilyl)prop-2-yn-1-yl acrylate) triblock copolymer containing functional groups were rapidly prepared via sequential addition of monomers without purification steps.

Chemoenzymatic synthesis of polymeric materials using lipases as catalysts: a review

In the past two decades, enzymatic polymerization has rapidly developed and become an important polymer synthesis technique. However, the range of polymers resulting from enzymatic polymerization could be further expanded through combination with chemical methods. This review systematically introduces recent developments in the combination of lipase-catalyzed polymerization with atom transfer radical polymerization (ATRP), kinetic resolution, reversible addition-fragmentation chain transfer (RAFT), click reaction and carbene chemistry to construct polymeric materials like block, brush, comb and graft copolymers, hyperbranched and chiral polymers. Moreover, it presents a thorough and descriptive evaluation of future trends and perspectives concerning chemoenzymatic polymerization. It is expected that combining enzymatic polymerization with multiple chemical methods will be an efficient tool for producing more highly advanced polymeric materials.

Photoredox catalyst-mediated atom transfer radical addition for polymer functionalization under visible light

A facile method for post-functionalization of polymers with side olefin groups was developed by visible light-mediated atom transfer radical addition (ATRA) employing a photoredox catalyst, fac-Ir(ppy)₃.

A facile one pot strategy for the synthesis of well-defined polyacrylates from acrylic acid via RAFT polymerization

Linear and hyperbranched polyacrylates were successfully synthesized by the combination of in situ esterification of acrylic acid with halogenated compounds promoted by 1,1,3,3-tetramethylguanidine (TMG) and RAFT polymerization.

One-Pot Cascade Synthetic Strategy: A Smart Combination of Chemoenzymatic Transesterification and Raft Polymerization

Enzymatic transesterification was combined with RAFT polymerization to develop a new one-pot synthetic method for new polymer synthesis. This method contained in situ monomer transformation reaction between acyl donor monomer and primary alcohols such as hexanol and so on, followed by subsequent RAFT polymerization to get target polymers. The enzymatic reaction and RAFT polymerization tolerated each other and cooperated well to get new polymers with a completely transformed new monomer, high polymer yields, excellent control over the polymerization process, and good enzyme activity maintenance, providing a general and straightforward methodology for new polymer synthesis and modification.