Hybrid Copolymerization Research Articles

Transforming Element Sulfur to High Performance Closed‐Loop Recyclable Polymer via Proton Transfer Enabled Anionic Hybrid Copolymerization

AbstractThe utilization of sulfur has been a global issue. Copolymerization of element sulfur (S8) with other monomers is a promising route to convert it to useful materials but is limited by the comonomers. Here, we report anionic hybrid copolymerization of S8 with acrylate and epoxide at room temperature, where S8 does not copolymerize with epoxide in the absence of acrylate. Yet, the proton transfer from the methyne in acrylate to the oxygen anion enables the ring‐opening of the cyclic comonomer and hence the copolymerization. The cyclic comonomers can be expanded to lactone and cyclic carbonate. Specifically, the copolymer of S8 with bisphenl A diglycidyl ether and diacrylate displays mechanical properties comparable to those of most common plastics, namely, it has ultimate tensile strength as high as 60.8 MPa and Young's modulus up to 680 MPa. It also exhibits high UV resistance and good transparency. Particularly, it has excellent UV‐induced self‐healing, reprocessability and closed‐loop recyclability due to the abundant dynamic S−S bonds and ester groups. This study provides an efficient strategy to turn element sulfur into closed‐loop recyclable polymer with high mechanical and optical performances.

Transforming Element Sulfur to High Performance Closed-Loop Recyclable Polymer via Proton Transfer Enabled Anionic Hybrid Copolymerization.

The utilization of sulfur has been a global issue. Copolymerization of element sulfur (S8) with other monomers is a promising route to convert it to useful materials but is limited by the comonomers. Here, we report anionic hybrid copolymerization of S8 with acrylate and epoxide at room temperature, where S8 does not copolymerize with epoxide in the absence of acrylate. Yet, the proton transfer from the methyne in acrylate to the oxygen anion enables the ring-opening of the cyclic comonomer and hence the copolymerization. The cyclic comonomers can be expanded to lactone and cyclic carbonate. Specifically, the copolymer of S8 with bisphenl A diglycidyl ether and diacrylate displays mechanical properties comparable to those of most common plastics, namely, it has ultimate tensile strength as high as 60.8 MPa and Young's modulus up to 680 MPa. It also exhibits high UV resistance and good transparency. Particularly, it has excellent UV-induced self-healing, reprocessability and closed-loop recyclability due to the abundant dynamic S-S bonds and ester groups. This study provides an efficient strategy to turn element sulfur into closed-loop recyclable polymer with high mechanical and optical performances.

Enzyme‐Responsive Polyion Complex Nanoparticles of Cationic Antimicrobials for Activatable Antibacterial Therapy

AbstractA self‐assembled “caging” strategy is presented for the safe delivery of potent cationic antimicrobials that suffer from non‐specific toxicity for the effective treatment of in vivo systemic bacterial infection. The key development here is a new block copolymer consisting of a poly(ethylene glycol) (PEG) stealth block and an anionic and lipase‐degradable block of poly(ɛ‐caprolactone) (PCL) and phosphonic acid‐bearing methacrylate copolymer, synthesized by hybrid copolymerization of methacrylate and cyclic esters. The anionic blocks electrostatically interact with cationic antimicrobials to form neutrally charged polyion complexes with the PEG blocks on the surface. The PCL component imparts the nanocomplex with biodegradability by bacterial secretory lipase. In the proof‐of‐concept study, cationic polyimidazolium that shows excellent antibacterial activity but severe toxicity is packaged by the block copolymer into nanocomplexes, which are stable in complex environments of high salt and protein concentrations and released the antimicrobials upon degradation of the copolymer by bacteria‐secreted lipase. The “caging” formulation of polyimidazolium eliminated its toxicity and led to highly effective bactericidal performance comparable to free polyimidazolium. This caging strategy does not require sophisticated chemical modification of cationic antimicrobials, offering a broadly applicable formulation strategy to overcome their common toxicity issue that has become a primary translational barrier.

2D ZIF-L(Zn) for Hybrid Copolymerization of Methyl Methacrylate and ε-Caprolactone under Solvent-free Medium

Herein, we report the hybrid copolymerization of methyl methacrylate (MMA) and ε-caprolactone (CL). 2D metal-organic frameworks, ZIF-L as a robust polymerization catalyst, can catalyze this hybrid copolymerization. Though these monomers differ from each other in structure and activity, different characterization techniques (1H-NMR, 13C-NMR, GPC, DSC, fractional precipitation techniques) confirm that they form biodegradable block copolymer PMMA-b-PCL with high molecular weight (1190 kg/mol). Also, PXRD and SEM results of the recovered ZIF-L reveal that the catalyst ZIF-L is remarkably stable even after a long-time polymerization reaction with no significant loss in activity.

Anionic Hybrid Copolymerization of Sulfur with Acrylate: Strategy for Synthesis of High-Performance Sulfur-Based Polymers.

Copolymerization of elemental sulfur (S8) with vinyl monomers to develop new polymer materials is significant. Here, for the first time, we report the anionic hybrid copolymerization of S8 with acrylate at 25 °C, yielding a copolymer with short polysulfide segments; i.e., each of them consists of only one to four sulfur atoms. The formation of a longer polysulfide segment would be ceaselessly disrupted by carbon anions through the chain-transfer reaction. The copolymer of S8 with diacrylate was cross-linked and exhibited excellent mechanical properties, with an ultimate tensile strength as high as 10.7 MPa and a breaking strain of 22%. Furthermore, the introduction of tertiary amide groups to the copolymer enabled it not only to be reprocessed via press molding at room temperature but also to exhibit self-healing properties without external intervention. This study provides a facile strategy to synthesize high-performance sulfur-based copolymers under mild conditions.

Revisiting the structure of copolymer via anionic hybrid copolymerization of methyl methacrylate and ε-caprolactone

Anionic hybrid copolymerization of vinyl and cyclic monomers provides a powerful strategy to synthesize heteropolymers. Yet, there are some open questions regarding its mechanism and the structure of the resulted polymer. We reported that the copolymer (Poly(MMA- co -CL)) of methyl methacrylate (MMA) and ε-caprolactone (CL) via such copolymerization was random. However, a recent study proposed that the copolymer might be simple graft one with poly(methyl methacrylate) (PMMA) as the main chain and poly(ε-caprolactone) (PCL) as the graft chain. In this study, we synthesized a model graft copolymer (PMMA- g -PCL) by using a combination of reversible complexation-mediated polymerization and ring-opening polymerization, and made comparison with Poly(MMA- co -CL) in their properties and hydrolysis. Differential scanning calorimeter (DSC) measurements show that the graft copolymer PMMA- g -PCL possesses two glass transitions and a melt peak. In contrast, Poly(MMA- co -CL) exhibits only one glass transition without a melt peak because it is amorphous, clearly indicating that it is random. Proton nuclear magnetic resonance ( 1 H NMR) measurements reveal that the hydrolysis of PMMA- g -PCL yields only PMMA oligomers. However, the hydrolyzed products of Poly(MMA- co -CL) consist of MMA and CL units. The facts further indicate that the copolymer Poly(MMA- co -CL) is random. Considering that the transesterification reactions are unavoidable in the anionic hybrid copolymerization, the copolymer should consist of random main chain and random branches. • The present study demonstrates that anionic hybrid copolymerization of MMA and CL generally yields random copolymer but not graft copolymer. • Transesterification is not the essential step in the anionic hybrid copolymerization, but it can cause branching of the copolymer. • The hybrid copolymer of MMA and CL consists random main chain and random branches.

Anionic Hybrid Copolymerization of Cyclic and Vinyl Monomers without Transesterification

AbstractAnionic hybrid copolymerization (AHcP) of cyclic and vinyl monomers provides a powerful strategy to synthesize biodegradable heteropolymers. However, transesterification between comonomeric units often happens making the mechanism complex. Here, AHcP of N,N‐dimethylacrylamide (DMA) with ε‐caprolactone (CL) is investigated at 25 °C, where DMA does not have ester group so that no transesterification between DMA and CL units happens. Nuclear magnetic resonance (NMR) and matrix‐assisted laser desorption/ionization time of flight mass spectrometry measurements reveal that DMA and CL units are randomly distributed in the resulted polymer. Differential scanning calorimetry measurements show that the copolymer has only one glass transition temperature (Tg). Thermogravimetric analysis demonstrates the copolymer has a single‐stage decomposition from 255 to 425 °C, which is between those of the corresponding homopolymers. Thes facts further indicate that the copolymer is random. This study clearly demonstrates that AHcP takes place regardless of transesterification though it may have some effects.

Degradable Vinyl Polymers for Combating Marine Biofouling.

Marine organisms such as barnacle larvae and spores of algae adhere to underwater surfaces leading to marine biofouling. This phenomenon has numerous adverse impacts on marine industries and maritime activities. Due to the diversity of fouling organisms and the complexity of the marine environment, it is a huge challenge to combat marine biofouling, which limits the development and utilization of marine resources. Since the International Marine Organization banned the use of tributyltin self-polishing copolymer (SPC) coatings in 2008, the development of an environmentally friendly and efficient anti-biofouling polymer has been the most important task in this field. Tin-free SPC is a well-established and widely used polymer binder for anti-biofouling coating today. Being a nondegradable vinyl polymer, SPC exhibits poor anti-biofouling performance in static conditions. Even more, such nondegradable polymers were considered to be a source of microplastics by the International Union for the Conservation of Nature in 2019. Recently, numerous degradable polymers, which can form dynamic surface through main chain scission, have been developed for preventing marine biofouling in static conditions. Nevertheless, the regulation of their degradation and mechanical properties is limited, and they are also difficult to functionalize. A new polymer combining the advantages of vinyl polymers and degradable polymers is needed. However, such a combination is a challenge since the former are synthesized via free radical polymerization whereas the latter are synthesized via ring-opening polymerization.In this Account, we review our recent progress toward degradable vinyl polymers for marine anti-biofouling in terms of polymerization methods and structures and properties of polymers. First, we introduce the strategies for preparing degradable vinyl polymers with an emphasis on hybrid copolymerization. Then, we present the synthesis and performance of degradable and hydrolyzable polyacrylates, degradable polyurethanes with hydrolyzable side groups, and surface-fragmenting hyperbranched polymers. Polymers with degradable main chains and hydrolyzable side groups combine the advantages of SPC and degradable polymers, so they are degradable and functional. They are becoming new-generation polymers with great potential for preparing high-efficiency, long-lasting, environmentally friendly and broad-spectrum coatings to inhibit marine biofouling. They can also find applications in wastewater treatment, biomedical materials, and other fields.

Hybrid copolymerization of acrylate and thiirane monomers mediated by trithiocarbonate

The composition and structure of polymers have great influence on their performances.

Hybrid Copolymerization of Ethylene Oxide and tert-Butyl Methacrylate with Organocatalyst.

Hybrid copolymerization of structurally different, reactivity and mechanism distinct monomers (e.g., cyclic and vinyl type monomers) is of great interest and challenge for both academic research and practical application. Herein, ethylene oxide-co-tert-butyl methacrylate-co-poly(ethylene glycol) benzyl methacrylate (EO-co-BMA-co-bPEO), a statistical copolymer was synthesized via hybrid copolymerization of EO and BMA using an uncharged, non-nucleophilic organobase t-BuP4 as the catalyst. Detailed characterizations indicate that hybrid copolymerization of ethylene oxide and vinyl monomer forms a statistical copolymer concurrently with the transesterification of tert-butyl group and oligomer PEO anions. The application of the copolymer as all solid lithium-ion battery polymer electrolyte was investigated by detecting the ionic conductivity (σ) with electrical impedance spectrum measurement.

Cooligomerization of γ-butyrolactone with (meth)acrylates catalyzed by N-heterocyclic carbene: Low possibility of hybrid copolymerization

Copolymerization between lactones and vinyl monomers has significant implications for the synthesis of new polymeric materials; however, a highly reactive cyclic monomer, e.g., ε-caprolactone (CL), leads to a copolymeric product but with a complex structure remaining to be elucidated. Herein, we present cooligomerizations of γ-butyrolactone (γBL), a low-polymerizable cyclic monomer, with (meth)acrylates catalyzed by an N-heterocyclic carbene (NHC) under conditions in which no reaction occurs in the absence of either comonomer. Several experimental studies indicate that the product is not a hybrid cooligomer with an ester linkage in the main chain but a graft cooligomer. The reaction mechanism involves the generation of the γBL enolate by the NHC to initiate oligomerizations of γBL and (meth)acrylates followed by the transesterification of oligo (γBL) with an ester unit of (meth)acrylates. These results prompted us to investigate the previously reported structure of copolymer of CL and methyl methacrylate obtained by a phosphazene base catalyst. The hydrolysis experiment revealed that the copolymeric product turned out not to be a hybrid random copolymer.

Dithiocarbamate-mediated controlled copolymerization of ethylene with cyclic ketene acetals towards polyethylene-based degradable copolymers

In this article, degradable polyethylene (PE)-based copolymers containing ester units in the backbone were prepared through the hybrid copolymerization of ethylene and cyclic ketene acetals (CKAs) mediated by dithiocarbamate successfully.

Hybrid Copolymerization via the Combination of Proton Transfer and Ring-opening Polymerization

Phosphazene base, t-BuP2, was employed to catalyze the proton transfer polymerization (PTP) of 2-hydroxyethyl acrylate (HEA), and PTP was further combined with ring-opening polymerization (ROP) to exploit a new type of hybrid copolymerization. The studies on homopolymerization showed that t-BuP2 was a particularly efficient catalyst for the polymerization of HEA at room temperature, giving an excellent monomer conversion. Throughout the polymerization, transesterification reactions were unavoidable, which increased the randomness in the structures of the resulting polymers. The studies on copolymerization showed that t-BuP2 could simultaneously catalyze the hybrid copolymerization via the combination of PTP and ROP at 25 °C. During copolymerization, HEA not only provided hydroxyl groups to initiate the ROP of e-caprolactone (CL) but also participated in the polymerization as a monomer for PTP. The copolymer composition was approximately equal to the feed ratio, demonstrating the possibility to adjust the polymeric structure by simply changing the monomer feed ratio. This copolymerization reaction provides a simple method for synthesizing degradable functional copolymers from commercially available materials. Hence, it is important not only in polymer chemistry but also in environmental and biomedical engineering.

Synthesis of sequence-controlled polymers via sequential multicomponent reactions and interconvertible hybrid copolymerizations

Synthesizing artificial polymers with precise sequence structures, such as their biological analogues, is a serious challenge and of great importance in polymer science. Recently, step-growth polymerization and chain growth polymerization have been the main synthesis methods for preparing artificial sequence-regulated polymers. However, it is difficult to obtain sequence-controlled polymers with sufficient molecular diversity via step-growth polymerization; on the other hand, chain-growth polymerization generally requires laborious repetitive monomer feeding. In this focus review, the sequential multicomponent reactions for preparing periodic sequence-controlled polymers with sufficient molecular diversity and complexity and the interconvertible hybrid copolymerizations producing hybrid multiblock copolymers rapidly in one pot are highlighted. We have developed sequential multicomponent reaction and interconvertible hybrid copolymerization methods to prepare sequence-controlled polymers. The sequential multicomponent reaction combines more than two different multicomponent reactions in one pot to prepare periodic sequence˗controlled polymers with sufficient molecular diversity. The interconvertible hybrid copolymerization method uses trithiocarbonate compounds to combine radical polymerization of vinyl monomers and anionic ring-opening polymerization of thiirane monomers, resulting in hybrid multiblock sequence-regulated polymers.

Hybrid Photo-induced Copolymerization of Ring-Strained and Vinyl Monomers Utilizing Metal-Free Ring-Opening Metathesis Polymerization Conditions.

We introduce the hybrid copolymerization of two disparate monomer classes (vinyl monomers and ring-strained cyclic olefins) via living photopolymerization. The living character of the polymerization technique (metal-free photo-ROMP) is demonstrated by consecutive chain-extensions. Further, we propose a mechanism for the copolymerization and analyze the copolymer structure in detail by high-resolution mass spectrometry.

Anionic Hybrid Copolymerization via Concurrent Oxa‐Michael Addition and Ring‐Opening Polymerizations

AbstractHere, a new type of anionic hybrid copolymerization is exploited via the concurrent oxa‐Michael addition of ethylene glycol and neopentyl glycol diacrylate and the ring‐opening polymerization of ε‐caprolactone. The hybrid copolymerization process and the resulting copolymers are characterized using nuclear magnetic resonance, size exclusion chromatography, differential scanning calorimetry measurements, and thermogravimetric analysis. The results show that the hybrid copolymerization can proceed smoothly under mild reaction conditions and that the synthesized copolymer contains ester and ether structures in the backbone, possibly endowing the polymers with good hydrophilicity and degradability. More importantly, the composition of the synthesized polymer can be easily adjusted by changing the monomer feed ratio, and the chain crystallization is significantly reduced due to the random copolymeric structure. This hybrid copolymerization reaction provides a new method for synthesizing degradable functional copolymers from commercially available materials. Hence, this polymerization is important not only in polymer chemistry but also in environmental and biomedical engineering.

Hybrid copolymerization via mechanism interconversion between radical vinyl-addition and anion ring-opening polymerization

Here, we report a new hybrid copolymerization via an interconvertible living free radical and anion ring-opening polymerization mechanism, in which the copolymerization of cyclic monomers and vinyl-type monomers can be achieved.

Zwitterionic Copolymerization of β‐Butyrolactone with Styrene

AbstractThe hybrid copolymerization of vinyl monomers with cyclic esters endows the formed copolymers new features, such as biodegradability and functionality. However, the recently reported hybrid copolymerizations are mainly based on polar vinyl monomers and cyclic esters catalyzed by organocatalysts. The copolymerization of non‐polar vinyl monomers with cyclic esters is still a challenge. In this work, the copolymerization of β‐butyrolactone (β‐BL) with styrene catalyzed by B(C6F5)3 in the absence of coinitiators is reported. The density functional theory studies suggest the formation of zwitterion between β‐BL and B(C6F5)3. It is found that β‐BL and styrene are concurrently copolymerized through the macro‐zwitterion intermediates. The obtained copolymers are carefully examined by 1H NMR, 2D 1H‐13C HMBC, differential scanning calorimetry, thermogravimetric analysis, hydrolysis experiments, as well as Brady's reagents.

Synthesis and properties of antifouling poly(CL-co-zDMAEMA) zwitterionic copolymer by one-step hybrid copolymerization.

A novel biocompatible and biodegradable copolymer was synthesized by one-step hybrid copolymerization of ε-caprolactone (CL) and 2-(N,N-dimethylamino) ethyl methacrylate (DMAEMA) employing (1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phophoranylidenamino]-2Λ5,Λ5-catenadi(phosphazene) (t-BuP4) as a catalyst. The as-synthesized copolymer was betainizated resulting in a zwitterionic copolymer poly(CL-co-zDMAEMA) and the structure of the zwitterionic copolymer was confirmed by the FT-IR, NMR, and XPS measurements. The results of dynamic light scattering (DLS) show that this zwitterionic copolymer can self-assemble into stable micelles. The results of quartz crystal microbalance with dissipation (QCM-D) analysis and MTT measurement suggest that this zwitterionic copolymer possess better protein resistance and lower cell cytotoxicity in vitro in comparison with the cationic copolymer. The pyrene solubilization measurement of copolymers poly(CL-co-zDMAEMA) indicates an excellent pyrene solubilization capacity. These zwitterionic polymer micelles can release drugs in response to specific signals, such as temperature, pH, and enzymes and have a potential application in drug delivery and gene therapy due to their good antifouling, low cytotoxicity and high pyrene solubilization.

Poly(l-lactide-co-2-(2-methoxyethoxy)ethyl methacrylate): A biodegradable polymer with protein resistance

We have synthesized poly(l-lactide-co-2-(2-methoxyethoxy)ethyl methacrylate) (LA-co-MEO2MA) containing both degradable and protein resistant units via hybrid copolymerization with (1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phophoranylidenamino]-2Λ5,Λ5-catenadi(phosphazene) (t-BuP4) as the catalyst. Nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) show that LA-co-MEO2MA is a random copolymer. The studies of quartz crystal microbalance with dissipation (QCM-D) demonstrate that the copolymer enzymaticlly degrades much faster than poly(l-lactide) (PLA) homopolymer due to its lower crystallinity. We have also investigated the adsorption of bovine serum albumin (BSA), lysozyme or fibrinogen on a LA-co-MEO2MA surface in real time by use of QCM-D and surface plasmon resonance (SPR). Our studies reveal that the polymer is protein resistant depending on MEO2MA content. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay experiments demonstrate that the polymer has a low cytotoxicity.