Divinyl Monomers Research Articles

Design and Control of Polymeric Network Architectures Based on Network Dimension Theory

AbstractA new design policy to synthesize nanogel molecules having desired dimensions under unperturbed state is proposed. Miniemulsion copolymerization of vinyl and divinyl monomers, both conventional free‐radical polymerization and ideal living polymerization, is used to illustrate the method. For the network formation dynamics, the newly proposed model that takes into account the size and structure dependence of cross‐linking/cyclization reactions is employed. The master curve relationship that indicates the maximum average dimensions for randomly cross‐linked networks is used as a guideline and the network dimension is controlled by the magnitude of network maturity index NMI, which is the average number of cycle rank per primary chain. By appropriately sizing the NMI, it is possible to synthesize network polymers with dimensions equal to or greater than the maximum dimensions achievable with a homogeneous, randomly cross‐linked network polymer of the same cycle rank and molecular weight. The current strategy of designing and controlling 3D size is applicable regardless of the reaction mechanism of network formation and will also be applied to the synthesis of macro‐gels.

Design of Unconventional Polymers with Thermal Contraction Units for High-Performance Dental Adhesives.

The coefficient of thermal expansion (CTE) of adhesives is considered to be a vital parameter for dental restoration due to the oral temperature fluctuation induced by hot and cold drinks in daily life. Even more challenging, the adhesives need to bond various materials with different CTE values, and mismatched thermal expansion at the interface of two materials will produce thermal stress and cause cracking, leading to bond failure. In this study, we designed and synthesized a divinyl monomer containing a dibenzocyclooctadiene (DBCOD) unit, which was incorporated into a commercial adhesive, Single Bond Universal (SBU) to prepare low CTE adhesives. The CTE value of the adhesives can be adjusted low to 6.5 ppm/K, which is much lower than that of pure SBU. Mimicking the real applying conditions, the composite resin columns were bonded to the zirconia ceramics as a dental crown with our designed adhesives, and the shear bond strength test was carried out before and after 10 000 thermal cycles between 5 and 55 °C. The shear bond strength of pure SBU retains 44.7% of its original value after 10 000 thermal cycles, while those low CTE adhesives retain 74.6% and 61.9% of shear bond strength due to less deformation and interfacial stress during thermocycling. The newly designed adhesives provide a persistent way to enhance the shear bond strength and achieve a long lifetime in tooth restoration.

Alternating Graft Copolymer Carrying PLA Graft Chains at Every Other Unit: Sequence Impacts on Crystallization Behaviors.

Alternating graft copolymers were precisely synthesized via selective cyclopolymerization of pendant-transformable divinyl monomer (1), post-polymerization modification via aminolysis with alkylamine, and ring-opening polymerization of l-lactide (LLA) from the hydroxy pendant group in alternating sequence. The poly(LLA) (PLLA) graft chain on the alternating copolymer gave a higher crystallization degree on the isothermal treatment than that on the random counterpart likely because of the periodic sequence. The comonomer pendant group from alkylamine in the aminolysis reaction in the alternating sequence affected the crystallization behaviors, and the oligoethylene glycol (OEG) group promoted the crystallization thanks to the larger free volume effect. As for the stereocomplex formation of the racemic mixture of enantiomeric PLLA and poly(d-lactide) (PDLA) chains, the alternating graft copolymer gave a higher degree of stereocomplex crystallization in the mixture with the enantiomer homopolymer than the random analogue.

Miktoarm star polylactic acid/polybutylene succinate and its coherent characteristics

Miktoarm stars possess unique molecular architectures which each polymer chain expresses its physico-chemical properties either individually or integratedly. Up to present, although various biodegradable copolyesters, especially poly(lactic acid) (PLA) and poly(butylene succinate) (PBS), are known, the miktoarm star PLA/PBS is still not investigated. The present work proposes the application of arm-first approach to prepare core-crosslinked miktoarm star of poly(lactic acid) and poly(butylene succinate) (CCS-PLA/PBS). By simply polymerizing the bromo‑terminated macroinitiators with divinyl monomers, PLA and PBS chains are fixed at a central core to allow polymeric core-shell nanoparticle formation. As thermal properties of PLA and PBS are different, the variation of PLA/PBS ratio in CCS initiates thermo-responsive performances under glass transition temperature (Tg) and melting temperature (Tm) of PLA and PBS. The present work shows how the combination of two biodegradable polyesters as CCS introduces a new type of responsive nanoparticle which can be expected for advanced materials in biological applications.

Generating dual structurally and functionally skin-mimicking hydrogels by crosslinking cell-membrane compartments

The skin is intrinsically a cell-membrane-compartmentalized hydrogel with high mechanical strength, potent antimicrobial ability, and robust immunological competence, which provide multiple protective effects to the body. Methods capable of preparing hydrogels that can simultaneously mimic the structure and function of the skin are highly desirable but have been proven to be a challenge. Here, dual structurally and functionally skin-mimicking hydrogels are generated by crosslinking cell-membrane compartments. The crosslinked network is formed via free radical polymerization using olefinic double bond-functionalized extracellular vesicles as a crosslinker. Due to the dissipation of stretching energy mediated by vesicular deformation, the obtained compartment-crosslinked network shows enhanced mechanical strength compared to hydrogels crosslinked by regular divinyl monomers. Biomimetic hydrogels also exhibit specific antibacterial activity and adequate ability to promote the maturation and activation of dendritic cells given the existence of numerous extracellular vesicle-associated bioactive substances. In addition, the versatility of this approach to tune both the structure and function of the resulting hydrogels is demonstrated through introducing a second network by catalyst-free click reaction-mediated crosslinking between alkyne-double-ended polymers and azido-decorated extracellular vesicles. This study provides a platform to develop dual structure- and function-controllable skin-inspired biomaterials.

Exploiting the Monomer-Feeding Mechanism of RAFT Emulsion Polymerization for Polymerization-Induced Self-Assembly of Asymmetric Divinyl Monomers.

We exploited the monomer-feeding mechanism of reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization to achieve the successful polymerization-induced self-assembly (PISA) of asymmetric divinyl monomers. Colloidally stable cross-linked block copolymer nanoparticles with various morphologies, such as vesicles, were directly prepared at high solids. Morphologies of the cross-linked block copolymer nanoparticles could be controlled by varying the monomer concentration, degree of polymerization (DP) of the core-forming block, and length of the macro-RAFT agent. X-ray photoelectron spectroscopy (XPS) characterization confirmed the presence of unreacted vinyl groups within the obtained block copolymer nanoparticles, providing a landscape for further functionalization via thiol-ene chemistry. Finally, the obtained block copolymer nanoparticles were employed as additives to tune the mechanical properties of hydrogels. We expect that this study not only offers considerable opportunities for the preparation of well-defined cross-linked block copolymer nanoparticles, but also provides important insights into the controlled polymerization of multivinyl monomers.

Dimensions of Large‐Sized Network Polymers Formed in Miniemulsion Polymerization

AbstractThe mean‐square radius of gyration of network polymers can be correlated with the graph diameter, and the fraction d of segments located in the diameter chain is used to investigate the dimensions of large‐sized network polymers whose cycle rank is over 103. A simplified Monte Carlo simulation model for the miniemulsion vinyl/divinyl copolymerization is used for the generation of large‐sized network polymers, assuming the classical chemical kinetics are valid. Both conventional free‐radical polymerization and living polymerization are considered, and the heterogeneity of network architecture is controlled by changing the reactivity ratio of double bond in divinyl monomer with respect to that in vinyl monomer. The network maturity index (NMI) which is the cycle rank per primary chain is used to represent the degree of development of the network architecture. As the NMI increases to be well‐developed, the calibrated d, defined by dc = d/fd where fd is a calibration constant that shows the degree of network heterogeneity, starts to follow the master curve. This characteristic behavior applies regardless of the polymerization mechanism and the heterogeneity of the formed network architecture. Detailed characteristics of the master curve and prospects for application to gel molecules are also discussed.

Radical Cyclocopolymerization of a Transformable Divinyl Monomer with a Monovinyl Monomer and Postpolymerization Modification for the Synthesis of AAB-Type Alternating Copolymers Composed of NIPAM and Vinyl Ether

Radical Cyclocopolymerization of a Transformable Divinyl Monomer with a Monovinyl Monomer and Postpolymerization Modification for the Synthesis of AAB-Type Alternating Copolymers Composed of NIPAM and Vinyl Ether

Crosslinking and Gelation of Polymer Brushes and Free Polymer Chains in a Confined Space during Controlled Radical Polymerization─A Computer Simulation Study

The confinement effect on crosslinking and gelation during controlled/living copolymerization of a monovinyl and a divinyl monomer was studied by Monte Carlo computer simulation using the dynamic lattice liquid method. The simulated reactions took place in plane-parallel slits of various widths for various grafting densities (GDs) and various initial initiator/crosslinker ratios ([X]0/[Ini]0). Monomers and crosslinkers were initially randomly distributed in the slit, but initiators were either anchored to one solid plane (polymer brushes) or randomly distributed (free chains). For brushes, the gel point (GP) depended on GD and [X]0/[Ini]0. The higher these parameters, the lower was the gel point. The gel point was also affected by the slit width. For free, nongrafted chains, the dependence of GP on slit width was negligible. For brushes, a nonuniform density of crosslinks was found, the highest density was close to the wall. This asymmetry was high at the gel point and decreased at higher conversions.

Efficient Copolymerization of Ethylene with Polar Divinyl Monomer by Phosphino‐Phenolate Nickel Catalyst†

Comprehensive SummaryDirect copolymerization of olefin with polar monomers via a coordination‐insertion mechanism appears as the most efficient and attractive method to prepare functionalized polyolefins. Herein, we carried out direct copolymerization of ethylene and allyl acrylate by a bulky phosphino‐phenolate nickel catalyst, in which high‐molecular‐weight copolymers bearing polar five‐membered and six‐membered ring structures were afforded. Comprehensive NMR and FT‐IR analyses revealed multiplex structure of the obtained copolymers, in which both the noncyclic structural units bearing pendant allyl moiety (A) as well as acrylate moiety (B) and the cyclic structural units, γ‐butyrolactones (C) and δ‐valerolactone (D) were found. Exhilaratingly, the content of different structural units of the produced copolymer could be tuned by adjusting the concentration of the comonomer. Moreover, we also proved that the nickel‐based catalyst could produce related copolymers with significantly enhanced copolymer molecular weights in the copolymerization of allyl acrylate and ethylene compared with the palladium‐based catalyst under the same conditions.

Precision syntheses of poly(NIPAM-alt-HEMA) and effects of the alternating sequence on thermoresponsive behaviors in water

An alternating copolymer of 2-hydroxyethyl methacrylate and N-isopropylacrylamide was synthesized via cyclopolymerization of a divinyl monomer and aminolysis transformation for studies of the sequence-dependent thermal responsiveness in water.

Exploring telogen chemical structure and reactivity when forming highly branched polyesters derived from ethylene glycol dimethacrylate homopolymerisation under transfer-dominated branching radical telomerisation (TBRT) conditions

Chain transfer agents with very different reactivities modify the structures of polymers formed by TBRT, leading to options to control branching levels, and polymer properties, using a single divinyl monomer.

Poly(N-vinylpyrrolidone)-Laponite XLG Nanocomposite Hydrogels: Characterization, Properties and Comparison with Divinyl Monomer-Crosslinked Hydrogels.

The present work investigates, for the first time, the synthesis and properties of some nanocomposite (NC) hydrogels obtained by the aqueous solution free radical polymerization of N-vinylpyrrolidone (NVP) in the presence of Laponite XLG (XLG) as a crosslinker, in comparison with the corresponding hydrogels prepared by using two conventional crosslinking divinyl monomers: N,N′-methylenebisacrylamide (MBA) and tri(ethylene glycol) divinyl ether (DVE). The structure and properties of the hydrogels were studied by FTIR, TEM, XRD, SEM, swelling and rheological and compressive mechanical measurements. The results showed that DVE and XLG are much better crosslinking agents for the synthesis of PNVP hydrogels than MBA, leading to larger gel fractions and more homogeneous network hydrogels. The hydrogels crosslinked by either DVE or XLG displayed comparable viscoelastic and compressive mechanical properties under the experimental conditions employed. The properties of the XLG-crosslinked hydrogels steadily improved as the clay content increased. The addition of XLG as a second crosslinker together with a divinyl monomer strongly enhanced the material properties in comparison with the hydrogels crosslinked by only one of the crosslinkers involved. The FTIR analyses suggested that the crosslinking of the NC hydrogels was the result of two different interactions occurring between the clay platelets and the PNVP chains. Laponite XLG displayed a uniform distribution within the NC hydrogels, the clay being mostly exfoliated. However, a small number of platelet agglomerations were still present. The PNVP hydrogels described here may find applications for water purification and in the biomedical field as drug delivery systems or wound dressings.

Postpolymerization Modification and Topological Structure Design of Poly(vinyl ether)s Based on the Selective Addition Reaction of Electrophilic Selenium Reagent and Divinyl Monomers

Postpolymerization Modification and Topological Structure Design of Poly(vinyl ether)s Based on the Selective Addition Reaction of Electrophilic Selenium Reagent and Divinyl Monomers

Alternating Terpolymers through Cyclopolymerization and Subsequent Orthogonal Functionalization.

A method for the synthesis of functionalized alternating copolymers by reversible deactivation radical polymerization was developed. Copolymerization by reversible addition-fragmentation chain transfer of hexenyl vinyl ether with a novel fluorinated divinyl monomer yields alternating cyclopolymers that can be chemoselectively modified by three distinct orthogonal functionalization reactions. Along the thiol-ene click reaction and amidation, a third functionalization was achieved via NHC-catalyzed transesterification or acylation resulting in a small library of ABC-type alternating terpolymers.

Alternierende Terpolymere durch Cyclopolymerisation und anschließende orthogonale Funktionalisierung

AbstractEs wurde eine Methode zur Synthese funktionalisierter alternierender Copolymere durch radikalische Polymerisation mit reversibler Deaktivierung entwickelt. Die Copolymerisation durch reversible Additions‐Fragmentierungs‐Kettenübertragung von Hexenylvinylether mit einem neuartigen fluorierten Divinylmonomer liefert alternierende Cyclopolymere, die chemoselektiv durch drei unterschiedliche orthogonale Funktionalisierungsreaktionen modifiziert werden können. Neben der Thiol‐En‐Click‐Reaktion und der Amidierung wurde eine dritte Funktionalisierung durch NHC‐katalysierte Umesterung oder Acylierung erreicht, womit eine kleine Bibliothek von alternierenden Terpolymeren vom ABC‐Typ dargestellt wurde.

Two-dimensional crystallization of cyclopolymers

Free-standing 2D polymer materials with graphene-like crystalline layers hold great promise for many state-of-art applications. However, their fabrication remains challenging. A ferrocene tethered cyclopolymer (pFcMMA) is synthesized via the free radical polymerization of a divinyl monomer in this work. PFcMMA has a high degree of cyclization, but is not a stereo-regular structure like most vinyl polymers synthesized in free radical polymerization. PFcMMA can crystallize on the surface to form 2D crystals, which is evidenced by the birefringence phenomena, DSC and XRD analysis, and microscopic observation. Powder XRD of crystalline pFcMMA shows sharp interlayer diffraction, indicative of a highly crystalline phase. The crystallization process is supposed to follow the nonclassic crystallization pathway, i.e. the orientation of cyclopolymer main chains followed by the conformation transition of the side groups to form 2D crystalline layers. Variable temperature XRD combined with DSC analysis and polarizing optical microscopic observation demonstrate that the 2D crystalline phase begins to transition to a 3D crystalline phase at about 45 °C, the latter has a melting point at about 60 °C. The solid-solid crystalline transition is reversible and without intermediate melting, and the 2D crystalline phase is more stable at room temperature than the 3D phase. It is rationalized that nucleation from solutions is predominantly an entropy-driven process, while interactions between side groups and those between far separated main chains also benefit the formation of 2D crystalline phase. The commonalities of the crystallization processes of cyclopolymers are discussed. • A ferrocene tethered cyclopolymer forms 2D crystals on water surface. • The 2D crystalline phase undergoes a reversible solid-solid transition. • The 2D form appears to be the stable form at room temperature. • Formation of a 3D crystal at higher temperatures is observed. • The 2D crystallization process is entropy driven benefiting from group interactions.

Homopolymer-block-Alternating Copolymers Composed of Acrylamide Units: Design of Transformable Divinyl Monomers and Sequence-Specific Thermoresponsive Properties.

In this work, we synthesized an acrylamide-based terpolymer that is a block copolymer composed of an AB alternating copolymer and a C homopolymer. The key to the unprecedented achievement is rational design of an acrylate-acrylamide divinyl monomer carrying CF3-substituted salicylic acid ester bonds (AAm-CF3) to realize the efficient and selective cyclopolymerization as well as the quantitative transformation of the resultant cyclorepeating units. The selectivity in the cyclopolymerization and the pendant transformation ability were evaluated through reactivity ratios of the corresponding model monomers and quantitative aminolysis reactions of the model compound. The cyclopolymerization via the photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) process with a macrochain-transfer agent and subsequent aminolysis reaction afforded the homopolymer-block-alternating copolymer. The sequence-controlled terpolymer exhibited a very unique thermal response behavior in water that was strikingly different from the corresponding sequence-uncontrolled terpolymers, such as homopolymer-block-statistical copolymers and all statistical terpolymers, despite the fact that the structure cannot be distinguished by 1H NMR.

P(OEGMA‐co‐LMA) hyperbranched amphiphilic copolymers as self‐assembled nanocarriers

AbstractWe report on the synthesis of novel amphiphilic hyperbranched copolymers, namely Hyperbranched‐[poly (ethylene glycol) methyl ether methacrylate‐co‐lauryl methacrylate] (H‐[P(OEGMA‐co‐LMA)]), obtained by reversible addition‐fragmentation chain transfer (RAFT) polymerization utilizing the divinyl monomer, ethylene glycol dimethacrylate (EGDMA) as the branching agent. Molecular characterization by size exclusion chromatography (SEC) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy indicated the success of the polymerization. The self‐assembly behavior in aqueous media was investigated by light scattering techniques and fluorescence spectroscopy. The hyperbranched copolymers form multimolecular aggregates of nanoscale dimensions with a low critical aggregation concentration. In addition, the model hydrophobic drug, curcumin (CUR), known also for its intrinsic fluorescence properties, was used in order to investigate the H‐[P(OEGMA‐co‐LMA)] copolymers drug encapsulation ability. Curcumin is successfully loaded into the polymeric nanoparticles, as confirmed by dynamic light scattering and UV–Vis spectroscopy. Interestingly, curcumin hydrophobic interactions with the hyperbranched copolymers result in more well‐defined co‐assembled nanostructures, in terms of size and size distribution. The mixed copolymer‐CUR nano‐assemblies consist of small size nanoparticles (<100 nm) which exhibit relatively high size uniformity, colloidal stability and fluorescent properties. Overall, results signify that the biocompatible H‐[P(OEGMA‐co‐LMA)] nanostructures could potentially serve as nanocarrier systems for drug delivery and bio‐imaging applications.

Self-regenerating zwitterionic hyperbranched polymer with tunable degradation for anti-biofouling coatings

Regeneration of zwitterionic surfaces is a promising strategy to combat biofouling. In this study, we have prepared degradable hyperbranched anti-biofouling polymers of methyl methacrylate, tertiary carboxybetaine ester (TCB), and divinyl monomers via reversible addition-fragmentation chain transfer (RAFT) polymerization. The degradation rate of such polymers is a function of the content or type of divinyl monomers. As the content of methacrylic anhydride (MAAH) increases, the degradation rate of the polymer becomes faster; whereas, a change of the divinyl monomers causes the degradation rate to follow a descending order: N,N′-adipic bis(diacetone acrylamide hydrazone) (DAA2H) > MAAH > ethylene glycol dimethacrylate (EGDMA). Antibacterial and anti-diatom assays show that the coatings inhibit the adhesion of the marine bacteria Pseudomonas sp. and the diatom Navicula incerta. The polymeric coating is expected to be applied in marine anti-biofouling.