Chain Transfer Living Radical Polymerization Research Articles

Preparation of nonmigratory flexible poly(vinyl chloride)-b-poly(n-butyl acrylate)-b-poly(vinyl chloride) via aqueous reversible deactivation radical polymerization in a pilot reactor

Industrially-viable nonmigratory internal plasticization of poly(vinyl chloride) (PVC) is achieved by synthesis of the block copolymer poly(vinyl chloride)-b-poly(n-butyl acrylate)-b-poly(vinyl chloride) (PVC-b-PBA-b-PVC) by aqueous single electron transfer degenerative chain transfer living radical polymerization (SET-DTLRP). The introduction of a temperature step (42 °C to 80 °C) in the synthesis of PVC-b-PBA-b-PVC block copolymers from PBA macroinitiators resulted in materials with better overall performance than the commercial flexible PVC. The resulting copolymers were fully characterized by 1H NMR, SEC, SEM, TGA, DSC and DMTA to determine the composition, molecular weight, dispersity, morphology, thermal and mechanical properties, and compared with those of commercial formulations prepared with PVC and dioctyladipate (DOA). Most importantly, the plasticizing moieties of the PVC-b-PBA-b-PVC block copolymers are covalently bonded to the polymer, resulting in no migration upon extraction under conditions where DOA is readily extractable. Unlike commercial materials, the PVC-b-PBA-b-PVC block copolymers showed that the properties remain intact after extraction with n-hexane.

Molar Mass Dispersity Control by Iodine-mediated Reversible-deactivation Radical Polymerization

Dispersity (Đ) of polymers has greatly effect on the properties of polymeric materials, and therefore how to control Đ is much important but still a great challenge in polymer synthesis, especially for reversible-deactivation radical polymerization (RDRP) strategy. Herein, we successfully developed a novel strategy to adjust Đ of polymers by visible light-controlled reversible complexation mediated living radical polymerization (RCMP) and combination of single-electron transfer-degenerative chain transfer living radical polymerization (SET-DTLRP) at room temperature. In RCMP system, 2-iodo-2-methylpropionitrile (CP-I) and ethyl 2-iodo-2-phenylacetate (EIPA) were used as alkyl iodide initiators, by using methyl methacrylate (MMA) as the model monomer and n-butylacrylate (BA) as end-capping reagent to regulate Đ of polymers. Subsequently, we successfully prepared the block copolymer PMMA-b-PBA with adjustable Đ by reactivating the polymer end-chains via SET-DTLRP in the presence of copper wire, which fully demonstrating that it is a promising strategy that can keep the "living" feature of polymers while regulating their molar mass dispersities easily.

A one-step fabrication and modification of HIPE-templated fluoro-porous polymer using PEG-b-PHFBMA macrosurfactant

Polymerized high internal phase emulsion (polyHIPE) monoliths have attracted much attention because of their ease of preparation, precise control of porous structure and useful properties. For many applications, such as chromatographic separation media, reactivity or absorptivity, post-modification of surface functional groups is required to achieve the desired functionality. However, for fluoro-polymers, it has been a challenge to fabricate high-performance foams with uniform porous structures using HIPE due to the lack of suitable surfactants to stabilize the fluorinated emulsions. In our work, we proposed a bottom-up approach where the same surfactant that stabilized the water droplets within the oil phase was used to control the solid foam surface chemistry. We employed reversible addition–fragmentation chain transfer living radical polymerization to synthesize amphiphilic-fluorinated macrosurfactant (mPEG5K-PHFBMA) to stabilize water-in-oil (W/O) HIPE. Using hexafluorobutyl methacrylate as the oil-phase monomer and divinylbenzene as the cross-linking agent, we achieved a one-pot preparation of polyHIPEs based upon poly(ethylene glycol) (PEG) with biocompatible pore surfaces and potential use in tissue engineering. The effects of amphiphilic macromolecular surfactant concentration, PHFBMA block length and initiator oil/water solubility on the emulsion droplet size, pore morphology, porous surface performance and mechanical properties were studied. The PEG modification on porous surface in the polyHIPE was also confirmed by a contact angle test and water uptake experiment. It was found that short-chain fluorinated materials demonstrated very little bioaccumulation potential and consequently better environmental safety attributes. The addition of PEG gave good biocompatibility, and the properties of these porous materials may have great potential in cell tissue engineering applications.

PVC/PBA random copolymers obtained by SET–DTLRP: Pressure effect on glass transition, rheology, and processing

A study of the effect of pressure on the glass transition and viscosity of poly(vinyl chloride) (PVC)–poly(butyl acrylate) random copolymers prepared by Single Electron Transfer–Degenerative Chain Transfer Living Radical Polymerization and able to act as self‐plasticized PVCs, is presented. The research has a dual purpose, as it focuses on polymer physics, as well as on applied polymer processing. Results of dynamic mechanical thermal analysis, pressure–volume–temperature (PVT), and extrusion capillary tests were combined, to analyze the additivity of the free volume and the effect of frequency and pressure on the glass transition of the copolymers, Tg. Free volume additivity, which is on the basis of self‐plasticization, was revealed by Tg and activation energy of flow, Ea, results. dTg/dP results were linked to the number of segments involved in the glass transition temperature. Using an ad hoc model, which involves parameters obtained by PVT and the activation energy of flow, the pressure‐viscosity coefficient was determined. This allowed estimating the viscosity as a function of the shear rate, the temperature and the pressure, offering suitable data to be employed in virtual injection molding. J. VINYL ADDIT. TECHNOL., 25:76–84, 2019. © 2018 Society of Plastics Engineers

Tuning the viscoelastic features required for 3D printing of PVC-acrylate copolymers obtained by single electron transfer-degenerative chain transfer living radical polymerization (SET-DTLRP)

Tuning the viscoelastic features required for 3D printing of PVC-acrylate copolymers obtained by single electron transfer-degenerative chain transfer living radical polymerization (SET-DTLRP)

Preparation of PEGylated polymeric nanoprobes with aggregation-induced emission feature through the combination of chain transfer free radical polymerization and multicomponent reaction: Self-assembly, characterization and biological imaging applications

Self-assembly of amphiphilic luminescent copolymers is a general route to fabricate fluorescent polymeric microparticles (FPMs). In this work, the FPMs with aggregation-induced emission (AIE) feature were fabricated via the combination of the chain transfer free radical polymerization and “one-pot” multicomponent reaction, which conjugated the aldehyde-containing AIE active dye AIE (CHO-An-CHO) and amino-terminated hydrophilic polymer (ATPPEGMA) using mercaptoacetic acid (MTA) as the “lock” molecule. The structure, chemical compositions, optical properties as well as biological properties of the PPEGMA-An-PPEGMA FPMs were characterized and investigated by means of a series of techniques and experiments in detail. We demonstrated the final copolymers showed amphiphilic properties, strong yellow fluorescence and high water dispersibility. Biological evaluation suggested that PPEGMA-An-PPEGMA FPMs possess low cytotoxicity and can be used for cell imaging. More importantly, many other AIE active FPMs are expected to be fabricated using the similar strategy because of the good substrate and monomer applicability of the multicomponent reaction and chain transfer living radical polymerization. Therefore, we could conclude that the strategy described in this work should be of great interest for fabrication of multifunctional AIE active nanoprobes for biomedical applications.

PVC/PBA random copolymers prepared by Living Radical Polymerization (SET–DTLRP): Entanglements and chain dimensions

For the first time PVC–PBA random copolymers were prepared by Single Electron Transfer–Degenerative Chain Transfer Living Radical Polymerization giving rise to homogeneous chains, in terms of PVC/PBA proportion. Dynamic viscoelastic measurements in the terminal zone allowed evaluating the entanglement plateau modulus value, GN0, for each composition. An equation based on a model that correlates GN0 to melt chain dimensions was used to fit the variation of GN0 with PBA concentration. Correspondingly, the entanglements number, the characteristic ratio and the packing length values of each copolymer were obtained. As a corollary, the characteristic ratio of PBA, never reported before, was also evaluated.

The effect of crystallites on the rheological properties of microphase‐separated PVC‐PBA‐PVC triblock copolymers obtained by single electron transfer‐degenerative chain transfer living radical polymerization

Linear and nonlinear rheological properties of poly(vinyl chloride) (PVC)‐poly(n‐butyl acrylate)‐PVC triblocks of different compositions, obtained by single electron transfer‐degenerative chain transfer living radical polymerization, are investigated, focusing on the effect of crystallites. Dynamic mechanical thermal analysis results show the existence of two glass transition temperatures, denoting microphase segregation. However, rather than phase separation, it is the presence of two types of crystals that melt at Tm1 = 127 ± 0.8°C and Tm2 = 185 ± 2°C, respectively, the factor that determines the rheological response of the copolymers. To the difference with PVC homopolymers, extrusion flow measurements at very low temperatures (T = 100°C) are possible with the copolymers. A change in the viscosity‐temperature dependence is observed below and above the lowest melting temperature. Notwithstanding the microphase separation and the presence of crystallites, experiments carried out in conditions similar to industrial processing reveal a remarkable viscosity reduction for our copolymers with respect to PVC obtained by single electron transfer‐degenerative chain transfer living radical polymerization, conventional PVC, and PVC/[diethyl‐(2‐ethylhexyl) phthalate] compounds. Extrudates free of surface instabilities are obtained at low extrusion temperatures, such as 90–100°C. J. VINYL ADDIT. TECHNOL., 21:24–32, 2015. © 2014 Society of Plastics Engineers

Micellization of St/MMA Gradient Copolymers: A General Picture of Structural Transitions in Gradient Copolymer Micelles

In this work, a gradient copolymer of styrene (St) and methyl methacrylate (MMA) is synthesized via reversible addition-fragmentation chain transfer living radical polymerization and its micellization behaviors in an acetone and water mixture are investigated by transmission electron microscopy, light scattering, and NMR spectroscopy. Three different kinds of transitions were found to coexist in a single system for the first time: a unimers to micelles transition, a star-like micelles to crew-cut micelles transition resulting from the shrinkage of micelles, and morphological transitions from spherical micelles to cylindrical micelles to vesicles. Our findings provide a general picture of structural transitions and relaxation processes in gradient copolymer micelles, which can lead to the development of novel materials and applications based on gradient copolymers.

Influence of the isomeric structures of butyl acrylate on its single‐electron transfer‐degenerative chain transfer living radical polymerization in water Catalyzed by Na2S2O4

AbstractThe aim of this work is to the study the influence of the isomer structures of butyl acrylate monomer on the single‐electron transfer/degenerative chain transfer mediated living radical polymerization (SET‐DTLRP). The kinetic of isobutyl acrylate is determined for the first time by SET‐DTLRP in water catalyzed by sodium dithionite. The plots of number‐average molecular weight versus conversion and ln([M]0/[M]) versus time are linear, demonstrating a controlled polymerization. The influence of the isomer t‐butyl, i‐butyl, and n‐butyl on the kinetics, properties, and stereochemistry of the reactions was assessed. To the best of our knowledge, there is no previous report dealing with the synthesis of PiBA by any LRP approach in aqueous medium. The results presented in this work suggest that the stability provided by the acrylate side group has an important influence in the polymerization process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6542–6551, 2008

Synthesis of poly(ethyl acrylate) by single electron transfer‐degenerative chain transfer living radical polymerization in water catalyzed by Na2S2O4

AbstractLiving radical polymerization of ethyl acrylate was achieved by single‐electron‐transfer/degenerative‐chain transfer mediated living radical polymerization in water catalyzed by sodium dithionite. The plots of number‐average molecular weight versus conversion and ln[M]0/[M] versus time are linear, indicating a controlled polymerization. This method leads to the preparation of α,ω‐di(iodo)poly(ethyl acrylate) (α,ω‐di(iodo)PEtA) macroinitiator that can be further functionalized. The molecular weight distributions were determined using a combination of three detectors (TriSEC): right‐angle light scattering, a differential viscometer and refractive index. The method studied in this work represents a possible route to prepare well‐tailored macromolecules made of ethyl acrylate in environmental friendly reaction medium. To the best of our knowledge there is no previous report dealing with the synthesis of PEtA by any LRP approach in aqueous medium. Furthermore, the method described in this article was successfully applied in pilot scale reactions under industrial production conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 421–432, 2008

Synthesis of Poly(lauryl acrylate) by Single‐Electron Transfer/Degenerative Chain Transfer Living Radical Polymerization Catalyzed by Na2S2O4 in Water

AbstractLiving radical polymerization of lauryl acrylate was achieved by SET/DTLRP in water catalyzed by sodium dithionite. The work describes the synthesis of a highly hydrophobic and polar monomer in aqueous medium. The plots of $\overline M _{\rm n}$ versus conversion and ln[M]0/[M] versus time are linear, indicating a controlled polymerization. This method leads to α,ω‐diiodopoly(lauryl acrylate)s that can be further functionalized. The MWDs were determined using a combination of three detectors: RALLS, DV, and RI. The method studied in this work represents a possible route to prepare well‐tailored macromolecules made of LA in environment friendly reaction medium. The syndiotactic content is 75%.magnified image

Thermal and mechanical characterization of poly(vinyl chloride)-b-poly(butyl acrylate)-b-poly(vinyl chloride) obtained by single electron transfer – degenerative chain transfer living radical polymerization in water

This work reports the synthesis of several copolymers of poly(vinyl chloride)-b-poly( n-butyl acrylate)-b-Poly(vinyl chloride) prepared by single electron transfer/degenerative chain transfer mediated living radical polymerization (SET-DTLRP) in a two step process: first, a bifunctional macroinitiator of α,ω-di(iodo)poly(butyl acrylate) [α,ω-di(iodo)PBA] was synthesized by SET-DTLRP in water at 30 °C. The obtained macroinitiator was further reinitiated also by SET-DTLRP leading to the formation of the desired product. Several copolymers were synthesized in a 5L pilot reactor with different molecular weights and relative amounts of PBA and PVC. The possibility of synthesizing flexible materials made of PVC without using normal free plasticizes is extremely important for the industry. After processing the materials in a two-roll mill laboratorial equipment, the block copolymers were characterized concerning thermal and mechanical. The materials characterized in this study were prepared in a 5L pilot reactor under similar conditions to be used in industrial scale.

Single electron transfer–degenerative chain transfer living radical polymerization of N‐butyl acrylate catalyzed by Na2S2O4 in water media

AbstractLiving radical polymerization of n‐butyl acrylate was achieved by single electron transfer/degenerative‐chain transfer mediated living radical polymerization in water catalyzed by sodium dithionate. The plots of number–average molecular weight versus conversion and ln[M]0/[M] versus time are linear, indicating a controlled polymerization. This methodology leads to the preparation of α,ω‐di(iodo) poly (butyl acrylate) (α,ω‐di(iodo)PBA) macroinitiators. The influence of polymerization degree ([monomer]/[initiator]), amount of catalyst, concentration of suspending agents and temperature were studied. The molecular weight distributions were determined using a combination of three detectors (TriSEC): right‐angle light scattering (RALLS), a differential viscometer (DV), and refractive index (RI). The methodology studied in this work represents a possible route to prepare well‐tailored macromolecules made of butyl acrylate in an environmental friendly reaction medium. Moreover, such materials can be subsequently functionalized leading to the formation of different block copolymers of composition ABA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2809–2825, 2006

Synthesis of ultrahigh molar mass, structural defects free poly(vinyl chloride) with high syndiotacticity and glass transition temperature by single electron transfer–degenerative chain transfer living radical polymerization (SET–DTLRP)

Synthesis of ultrahigh molar mass, structural defects free poly(vinyl chloride) with high syndiotacticity and glass transition temperature by single electron transfer–degenerative chain transfer living radical polymerization (SET–DTLRP)