Single Electron Transfer-degenerative Chain 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.

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)

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.

Scaling-up of poly(vinyl chloride) prepared by single electron transfer–degenerative chain transfer mediated living radical polymerization in water media—II: High molecular weight-ultra stable PVC

This work reports the preparation and study of poly(vinyl chloride) (PVC) with medium and high molecular weight using a Living Radical Polymerization (LRP) method in aqueous systems. The synthesis of ultra thermal stable PVC that falls outside the typical values known for the PVC industry is presented and PVC thermal stability is evaluated using a standard industrial method. The results presented in this manuscript suggest that the single electron transfer–degenerative transfer mediated living radical polymerization (SET–DTLRP) mechanism is the main factor influencing the thermal stability, since the polymerization temperature has no detectable effect on this property. In contrast to the Free Radical Polymerization (FRP), where low temperatures lead to PVC with high thermal stability that corresponds to a high molecular weight polymer, the polymerization temperature in SET–DTLRP (range 21–42 °C) has no detectable effect on the thermal stability of PVC. The final molecular weight is defined by the [monomer] 0/[initiator] 0 ratio (degree of polymerization). The PVC synthesis reported in this manuscript was carried out in a 150 L pilot reactor, which represents a reliable approach in terms of hydrodynamic conditions, when compared with those at the industrial scale.

Particle features and morphology of poly(vinyl chloride) prepared by living radical polymerisation in aqueous media. Insight about particle formation mechanism

The aim of this work is to evaluate PVC resins prepared by Single Electron Transfer Degenerative Chain Transfer Living Radical Polymerisation (SET-DTLRP) in a 150 L reactor under industrial conditions. The product features were analysed considering the standard resin features of PVC prepared by the conventional free radical polymerisation (FRP) method. It was proved that the FRP and SET-DTLRP have different particle growing mechanism and led to grains with completely different features (particle size, particle size distribution and morphology). It is critical for the PVC producers the preparation of PVC with a predetermined grain shape, particle size distribution and porosity which have an indubitable influence on polymer processing. It is presented a detailed study on the particle formation of the PVC synthesised by SET-DTLRP providing first insights into PVC features associated with a new polymerisation technique taking into account the normal requirements of the PVC industry. A possible mechanism of the SET-DTLRP particle formation is proposed.

Scaling-up of poly(vinyl chloride) prepared by single electron transfer degenerative chain transfer mediated living radical polymerization in water media: 1) Low molecular weight. Kinetic analysis

This paper reports the kinetic study of the scale-up for the production of PVC by using a single electron transfer degenerative chain transfer mediated living radical polymerization in water media in a 150 L reactor. It presents the study of several parameters that have an important role in the reaction kinetics (initiators, suspending agents, catalysts and temperature). The thermal stability of the materials was also assessed using a standard discoloration test employed by the PVC industry. The results show the possibility of scaling-up this new and promising technology using the same facilities as the conventional free radical polymerization process with results closely matching those obtained in 50 mL glass reactors.

Synthesis of high glass transition temperature copolymers based on poly(vinyl chloride) via single electron transfer—Degenerative chain transfer mediated living radical polymerization (SET‐DTLRP) of vinyl chloride in water

Abstractα,ω‐di(iodo) poly(isobornyl acrylate) macroiniators (α,ω‐di(iodo)PIA) with number average molecular weight from Mn,TriSEC = 11,456 to Mn,TriSEC = 94,361 were synthesized by single electron transfer‐degenerative chain transfer mediated living radical polymerization (SET‐DTLRP) of isobornyl acrylate (IA) initiated with iodoform (CHI3) and catalyzed by sodium dithionite (Na2S2O4) in water at 35 °C. The plots of number average molecular weight vs conversion and ln{[M]0/[M]} vs time are linear, indicating a controlled polymerization. α,ω‐di(iodo) poly(isobornyl acrylate) have been used as a macroinitiator for the SET‐DTLRP of vinyl chloride (VCM) leading to high Tg block copolymers PVC‐b‐PIA‐b‐PVC. The dynamic mechanical thermal analysis of the block copolymers suggests just one phase indicating that copolymer behaves as a single material. This technology provides the possibility of synthesizing materials based on PVC with higher Tg in aqueous medium. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009

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)

Phase transfer catalyzed single electron transfer–degenerative chain transfer mediated living radical polymerization (PTC‐SET–DTLRP) of vinyl chloride catalyzed by sodium dithionite and initiated with iodoform in water at 43 °C

AbstractTo accelerate the living radical polymerization (LRP) of vinyl chloride (VC) in water the phase transfer catalyzed single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of VC mediated by sodium dithionite (Na2S2O4) was investigated. The fastest polymerization reaction that still produces thermally stable poly(vinyl chloride) (PVC) takes place at 43 °C with the ratio [PTC]0/[Na2S2O4]0 = 0.0075/1. Cetyltrimethylammonium bromide (nC16H33(CH3)3N+Br−, CetMe3NBr) was the phase‐transfer catalyst (PTC) of choice. Under these conditions the first, fast stage of SET–DTLRP of VC was accomplished within 7–8 h when the initial ratio monomer/initiator [VC]0/[CHI3]0 was 800. The number‐average molecular weight (Mn) of the resulting PVC was in good agreement with the theoretical molecular weight (Mth). When the [VC]0/[CHI3]0 ratio was 4800, the fast step of the reaction was accomplished within 17 h, to produce 72% monomer conversion. A deviation of the Mn from the Mth was observed in this case. Possible mechanistic explanations for this deviation as well as for the phase transfer catalyzed SET–DTLRP of VC were suggested. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 779–788, 2005

Single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride initiated with methylene iodide and catalyzed by sodium dithionite

AbstractSingle electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride (VC) initiated with methylene iodide (CH2I2) and catalyzed by sodium dithionite (Na2S2O4) in water at 35 °C produces a telechelic poly(vinyl chloride) (LRP–PVC) with two different active chain ends: ICH2(CH2CHCl)n‐1CH2CHClI, and 2.0 functionality. The reactivity and initiator efficiency of CH2I2 in SET–DTLRP of VC was lower than those of iodoform. A possible mechanism for the CH2I2‐initiated SET–DTLRP of VC was suggested. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 773–778, 2005

Acceleration of the single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride in water at 25 °C

AbstractThe accelerated single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride (VC) in H2O/tetrahydrofuran (THF) at 25 °C is reported. This process is catalyzed by sodium dithionite (Na2S2O4)‐sodium bicarbonate (NaHCO3). Electron transfer cocatalysts (ETC) 1,1′‐dialkyl‐4,4′‐bipyridinum dihalides or alkyl viologens were also employed in this polymerization. The resulting poly(vinyl chloride) (PVC) has a number‐average molecular weight (Mn) = 2,000–12,000, no detectable amounts of structural defects, and both active chloroiodomethyl and inactive chloromethyl chain ends. The molecular weight distribution of PVC obtained is Mw/Mn = 1.5. The surface active agents afford the final polymers as a powder and provide an acceleration of the rate of polymerization. The role of ETC is to accelerate the single electron transfer (SET) step, whereas THF enhances the degenerative chain transfer (DT) step. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6364–6374, 2004