Effects of solvent basicity on free radical polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane initiated by barbituric acid

The polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane (BMI) initiated by barbituric acid (BTA) carried out in a variety of solvents at 130°C were studied. The nitrogen‐containing cyclic solvents such as N‐methyl‐2‐pyrrolidinone acted as a catalyst to promote the formation of the three‐dimensional crosslinked network structure. By contrast, the polymerization in a cyclic solvent that did not contain nitrogen such as γ‐butyrolactone resulted in nil gel content. The higher the solvent basicity, the larger the amount of insoluble polymer species formed. The molar ratio of BTA to BMI also played an important role in the polymerizations. The resultant polymers, presumably having a hyper‐branched structure, exhibited much narrower molecular weight distributions than those prepared by conventional free radical polymerizations. The BMI polymerizations using BTA as the initiator could not be adequately described by conventional free radical polymerization mechanisms. A polymerization mechanism that took into account the generation of a ketone radical pair between BTA and BMI and the subsequent initiation, propagation and termination reactions was proposed. It was concluded that the nitrogen‐containing cyclic solvents were capable of participating in the ketone radical pair formation process, thereby increasing the extent of polymer crosslinking reactions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Some Novel Features of the Oxidative Polymerization of N-Vinylcarbazole by Vanadium (V) Ion in Aqueous Medium

Oxidative polymerization of N-vinylcarbazole (NVC) was achieved in an aqueous suspension by vanadium (V) ion as the oxidant. Formation of polyN-vinylcarbazole (PNVC) was confirmed by Fourier transformed infrared (FTIR) spectroscopic analyses. Scanning electron microscopic (SEM) analyses of PNVC showed distinctive morphological pattern. Thermogravimetric stability studies (TGA/DTA) revealed that PNVC underwent about 60% weight loss up to 1,000°C temperature and suggested the formation of a structure different from that of conventional PNVC homopolymer soluble in solvents. PNVC obtained from the present study of NVC-V^V polymerization system was found to be intractable in nature and confirmed to be due to the formation of a cross-linked polymer structure. A possible pathway for the polymerization of NVC is via coupling of aromatic rings vis-à-vis in situ formation of cross-linked PNVC (CLPNVC) has been proposed.     

Syndiotactic‐specific radical polymerization of N‐isopropylacrylamide in toluene at low temperatures in the presence of silyl alcohols

The radical polymerization of N‐isopropylacrylamide was carried out in toluene at low temperatures in the presence of silyl alcohols, such as triethylsilanol. Poly(N‐isopropylacrylamide) with a racemo dyad content of 75% was obtained at ? 80 °C with a 4:1 triethylsilanol to monomer ratio loading. NMR analysis suggests that the mechanism for syndiotactic induction, in the presence of silyl alcohols, may be similar to that observed with alkyl alcohols. In this case, a 1:2 complex formation, via hydrogen bonding interactions, leads to the induction of syndiotactic specificity. Copyright © 2012 Society of Chemical Industry     

Synthesis and characterization of a novel hyperbranched polyether

A hyperbranched polyether has been synthesized by a single‐step nucleophilic displacement polymerization technique between cyanuric chloride and the sodium salt of bisphenol‐A. The effects of various reaction parameters on the yield, and molecular weight, as measured by the intrinsic viscosity of the polymer, have been studied. The synthesized polymer has been characterized by FT‐IR, UV and ¹H NMR spectroscopies, elemental analysis, solubility and viscosity measurements. The polymer is soluble in highly polar solvents such as N,N‐dimethylacetamide, N,N‐dimethylformamide and dimethyl sulfoxide, partially soluble in dilute aqueous NaOH solution, methanol, ethanol, chloroform, etc., but insoluble in water and non‐polar hydrocarbon solvents. The solubility parameter of the hyperbranched polymer has also been measured experimentally. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of homogeneously sulfonated poly(ether ether ketone) membranes: Effect of casting solvent

Poly(ether ether ketone) (PEEK) was homogeneously sulfonated to have various degrees of sulfonation from 48 to 83%. The sulfonated PEEK (sPEEK) membranes were prepared by a solvent casting method using a few solvents such as N,N‐dimethyl formamide, N,N‐dimethyl acetamide, and 1‐methyl‐2‐pyrrolidinone. The effect of casting solvent on the membrane morphology and properties was investigated. The sulfonation degree and ion exchange capacity were determined by a back titration method, and the morphology of membrane by SEM. It has been demonstrated that the surface morphology and properties of sPEEK membranes, such as water uptake, methanol permeability, ion conductivity, and mechanical strength, were considerably affected by the type of solvent, where the DMAC‐sPEEK system showed the best performance in the polymer electrolyte membrane application for DMFC. This solvent effect on the membrane morphology and properties was caused by interaction strength (hydrogen bonding) between polymer and solvent. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Temperature‐responsive characteristics of poly(N‐isopropylacrylamide) hydrogels with macroporous structure

Macroporous poly(N‐isopropylacrylamide) (PNIPA) hydrogels were synthesized by free‐radical crosslinking polymerization in aqueous solution from N‐isopropylacrylamide monomer and N,N‐methylenebis (acrylamide) crosslinker using poly(ethylene glycol) (PEG) with three different number‐average molecular weights of 300, 600 and 1000 g mol^?1 as the pore‐forming agent. The influence of the molecular weight and amount of PEG pore‐forming agent on the swelling ratio and network parameters such as polymer–solvent interaction parameter (χ) and crosslinking density (ν_E) of the hydrogels is reported and discussed. Scanning electron micrographs reveal that the macroporous network structure of the hydrogels can be adjusted by applying different molecular weights and compositions of PEG during polymerization. At a temperature below the volume phase transition temperature, the macroporous hydrogels absorbed larger amounts of water compared to that of conventional PNIPA hydrogels, and showed higher equilibrated swelling ratios in aqueous medium. Particularly, the unique macroporous structure provides numerous water channels for water diffusion in or out of the matrix and, therefore, an improved response rate to external temperature changes during the swelling and deswelling process. These macroporous PNIPA hydrogels may be useful for potential applications in controlled release of macromolecular active agents. Copyright © 2006 Society of Chemical Industry     

Group Selective Linear Polymerization of Vinyl Acrylate Using 19-Borabicyclo[3.3.1]nonane

Vinyl acrylate (VA) was polymerized with 9-borabicyclo[3.3.1]nonane (9-BBN) in tetrahydrofuran under argon at low temperatures (to -60°C). Hydroquinone and 2,6-di-tert-butyl-p-cresol had little effect on the polymerization. Addition of tetrachloromethane as a radical chain transfer agent did not lead to decrease in molecular weight of the polymer obtained. The initial rate of polymerization was proportional to [9-BBN]^0·91 and [VA]^1·37. The experimental results were indicative of non-radical properties of the propagating chain end. The polymer was soluble in organic solvents such as toluene, chloroform and N,N-dimethylformamide. The nuclear magnetic resonance measurements showed the presence of pendant vinyl groups in the polymer, indicating that only the acrylic double bond of VA reacted for polymerization to yield a linear polymer. Aniline retarded the polymerization and no polymer was formed in the presence of triethylamine. These inhibitory effects were explained on the basis of complex formation of 9-BBN with amines. This polymerization is discussed in terms of a non-radical mechanism. © of SCI.     

The use of biodiesel as a green polymerization solvent at elevated temperatures

BACKGROUND: Many important polymers are produced via solution polymerization. The solvent maintains a low viscosity, which provides many practical advantages related to heat transfer, mixing and material handling. Despite these advantages, commonly used solvents often present health and environmental problems. In an effort to replace these toxic solvents, a ‘green’ polymerization solvent, namely canola‐based FAME (fatty acid methyl ester or biodiesel), was used for solution polymerizations at an elevated temperature. RESULTS: Homopolymerizations of methyl methacrylate, styrene, butyl acrylate and vinyl acetate in FAME were studied at different solvent concentrations at 120 °C. Chain transfer to solvent rate constants (C_fs) were obtained for each polymer system and Arrhenius parameters for C_fs, i.e. E_a and A, were also calculated. These new solvent data were employed in a polymerization simulator to predict rate of polymerization and number‐ and weight‐average molecular weights for these commercially important systems. Model predictions showed reasonable agreement with experimental data. CONCLUSION: FAME fulfills the demands as a polymerization solvent. From an ecological perspective, FAME provides an environmentally friendly alternative to common solvents. From an industrial perspective, using FAME as a high‐boiling polymerization solvent can increase productivity by enabling polymerizations at elevated temperatures. Copyright © 2008 Society of Chemical Industry     

Using hydroxypropyl‐β‐cyclodextrin for the preparation of hydrophobic poly(ketoethyl methacrylate) in aqueous medium

This work was committed to the polymerization of hydrophobic ketoethyl methacrylate monomer in aqueous medium in the presence of cyclodextrin, instead of polymerizing the monomer in toxic and volatile organic solvents. For this purpose, a new ketoethyl methacrylate monomer, p‐methylphenacylmethacrylate (MPMA), was synthesized from the reaction of p‐methylphenacylbromide with sodium methacrylate in the presence of triethylbenzylammonium chloride. The monomer was identified with FTIR, ¹H and ¹³C‐NMR spectroscopies. Hydroxypropyl‐β‐cyclodextrin (HPCD) was used to form a water‐soluble host/guest inclusion complex (MPMA/HPCD) with the hydrophobic monomer. The complex was identified with FTIR and NMR techniques and polymerized in aqueous medium using potassium persulfate as initiator. During polymerization the resulting hydrophobic methacrylate polymer precipitated out with a majority of HPCD left in solution and a minority of HPCD bonded on the resulting polymer. The thus‐prepared polymer exhibited little difference from the counterparts obtained in organic solvent in number average molecular weight (M_n), polydispersity (M_w/M_n) and yield. The investigation provides a novel strategy for preparing hydrophobic ketoethyl methacrylate polymer in aqueous medium by using a monomer/HPCD inclusion complex. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of hydrogels by polymerization of itaconic acid–choline chloride deep eutectic solvent

Itaconic acid (IA)–choline chloride (CC) deep eutectic solvents (DES) were prepared and characterized by NMR, TGA, and DSC. Poly(itaconic acid–co–bisacrylamide) hydrogels were synthesized by in situ polymerization‐crosslinking of the DES. For comparison, the hydrogels were also prepared in water under the same process conditions, that is, temperature, time, initial concentration of the monomer, the initiator, and N,N′‐methylenebisacrylamide (BAA) as the cross‐linking agent. Chemical structure of the polymers was proved by elemental analysis and FTIR. The values of insoluble gel fraction and water swelling of obtained hydrogels suggest that polymers prepared in DES have higher cross‐link density. Preliminary comparative studies of polymerization of IA in water and in DES medium indicated higher polymerization rate resulting from the presence of the choline salt, what might explain properties of the hydrogels prepared in DES. This study shows that DES can be used both as a solvent and catalyst in free‐radical polymerization processes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40608.     

Temperature‐sensitive membranes prepared by the plasma‐induced graft polymerization of N‐Isopropylacrylamide into porous polyethylene membranes

A temperature‐responsive polymer, poly(N‐isopropylacrylamide) (PNIPAAm), was grafted onto porous polyethylene membranes by a plasma‐induced graft polymerization technique. A wide range of grafting was achieved through variations in the grafting conditions, including the postpolymerization temperature, time, monomer concentration, and graft‐reaction medium. The active species induced by plasma treatment was proven to be long‐living via a postpolymerization time of 95 h. Different solvent compositions, that is, water, methanol, benzene, and water/methanol, were used as reaction media, and water showed a much higher polymerization rate than the organic solvents. Based on the hydrophilicity of the active species, a mechanism explaining the solvent effect in plasma‐induced graft polymerization was examined. Characterizations by scanning electron microscopy, X‐ray photoelectron spectroscopy (XPS), and micro Fourier transform infrared showed that the grafted polymers were located on both the outer surface and inside pores of the membranes. The XPS analysis also confirmed that the polar amide groups tended to distribute more outward when grafted PNIPAAm was in its expanding state than when it was in its shrinking state. Water permeation experiments showed that the permeability of the grafted membranes varied dramatically with a slight temperature change in the vicinity of the lower critical solution temperature (LCST) of PNIPAAm. The effective pore radii of the grafted membranes above and below the LCST could be depicted by Hagen‐Poiseuille's law. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3180–3187, 2003     

Preparation of monodisperse hydrophilic polymer microspheres with N,N′‐methylenediacrylamide as crosslinker by distillation precipitation polymerization

Highly crosslinked cauliflower‐like poly(N,N′‐methylenebisacrylamide) particles were prepared by distillation precipitation polymerization in neat acetonitrile with 2,2′‐azobisisobutyronitrile as initiator. Monodisperse hydrophilic polymer microspheres with various functional groups, such as amide, pyrrolidone and carboxylic acid, with a spherical shape and smooth surface in the size range 120–600 nm were prepared by distillation precipitation copolymerizations of functional comonomers including N‐isopropylacrylamide, N‐vinylpyrrolidone, methacrylic acid with N,N′‐methylenebisacrylamide as crosslinker. The polymer particles were formed and precipitated out from the reaction medium during the distillation of the solvent from the reaction system through an entropic precipitation manner. The effects of the solvent and the degree of crosslinking on the morphology and the loading capacity of the functional groups of the resultant polymer particles were investigated. The resulting polymer particles were characterized with scanning electron microscopy, transmission electron microscopy, dynamic light scattering and Fourier transform infrared spectroscopy. Copyright © 2007 Society of Chemical Industry     

Synthesis of ultrahigh molecular weight phenolic polymers by enzymatic polymerization in the presence of amphiphilic triblock copolymer in water

An enzymatic oxidative polymerization of phenols was investigated in the presence of poly(ethylene glycol) (PEG)-poly(propylene glycol) (PPG)-poly(ethylene glycol) (PEG) triblock copolymer (Pluronic) in water. The formation of micellar aggregate of phenol and Pluronic by hydrogen bonding interaction in an aqueous solution was verified by DLS measurement. The PEG content of Pluronic greatly affected the polymerization behaviors. Using Pluronic with high PEG content improved the regioselectivity of the polymerization of phenol to give the polymer mainly consisting of phenylene unit. The polymerization in the presence of Pluronic F68 (EG₇₆-PG₂₉-EG₇₆) produced the phenolic polymer with ultrahigh molecular weight (M_w > 10⁶). From other phenols, high molecular weight polymers were also obtained. In addition, the FT-IR, DSC, and XRD analyses exhibited the formation of miscible complex between the phenolic polymer and Pluronic by hydrogen bonding interaction.     

Oxidative polymerization of N‐vinylcarbazole in polymer matrix

A new class of soluble conductive poly(N‐vinylcarbazole) (PVCz) compounds has been developed by oxidative matrix polymerization of N‐vinylcarbazole (NVCz) by Ce(IV) in the presence of poly(ethylene glycol) (PEG). PEG was found to be a more suitable matrix with which to obtain a stable homogenous ternary complex solution when compared with poly(acrylic acid) (PAA) and poly(vinylpyrrolidone) (PVP). The role of PEG, NVCz and Ce(IV) concentration, order of component addition, the structure of the polymer matrix, molecular weight of polymer and the effect of solvent have been investigated. Obtaining soluble PEG–Ce(III)–PVCz ternary complexes was shown by cyclic voltammetric measurements, and the initial rate of formation NVCz cation radicals as calculated using UV–visible spectrophotometry. Advantageously with these soluble complexes, conductivities could be measured both in solution and in the solid state. © 2001 Society of Chemical Industry     

N-乙烯基吡咯烷酮的自由基溶液聚合

考察了溶剂、单体浓度、引发剂等因素对N -乙烯基吡咯烷酮 (NVP)自由基聚合反应的影响 ,以苯、95%乙醇、蒸馏水为对象 ,重点考察了溶剂极性、单体与溶剂混合液黏度对NVP聚合反应速率、链增长速率常数及聚合物相对分子质量等的影响 .并进一步探讨了NVP与N ,N -亚甲基双丙烯酰胺在溶剂中的交联反应特性 ,发现某些无机盐水溶液有利于NVP的交联聚合反应 ,并用“笼蔽效应”作了解释 .     

Study on microemulsion polymerization of N‐butyl maleimide

By using sodium dodecyl sulfate (SDS) as an emulsifier, polymerization of N‐butyl maleimide (NBMI) was carried out in ternary oil‐in‐water microemulsion, initiated with potassium persulfate (KPS). The kinetics of microemulsion polymerization were measured by dilatometry. The effects of initiator concentration, polymerization temperature, monomer concentration, and emulsifier concentration on polymerization kinetics were investigated. On this basis, the polymerization kinetics were discussed. The experiment result showed that the microemulsion polymerization kinetics of N‐butyl maleimide were almost consistent with the prediction of the Smith‐Ewart theory in conventional emulsion polymerization, except that the emulsifier showed a special effect on polymerization. At the same time, the polymer was characterized by IR, ¹H‐NMR, DSC, and TGA. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 805–809, 2000     

Synthesis of syndiotactic poly(methacrylic acid) by free‐radical polymerization of the pseudo‐divinyl monomer formed with methacrylic acid and catechol

Syndiotactic poly(methacrylic acid) (Syn‐PMAA, r diad = 91 mol %) was synthesized by free radical polymerization of methacrylic acid (MAA) with catechol. The pseudo‐divinyl monomer was formed with one catechol and two MAA molecules by the hydrogen bonding between OH groups of catechol and COOH group of MAA. When the free radical polymerization of the pseudo‐divinyl monomer was carried out, intra‐ and intermolecular addition proceeded with racemic addition. The hydrogen bonding was the driving force to control tacticity. We discussed the effects of solvent, temperature, and the concentrations of MAA and catechol on the pseudo‐divinyl monomer formation. The highly syndiotactic PMAA was successfully obtained. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Reverse atom transfer radical polymerization of acrylonitrile

FeCl₃ coordinated by succinic acid was used as the catalyst for the first time in azobisisobutyronitrile‐initiated reverse atom transfer radical polymerization of acrylonitrile (AN). N,N‐dimethylformamide (DMF) was used as a solvent to improve the solubility of the ligand. A FeCl₃ to succinic acid ratio of 0.5 not only gives the best control of molecular weight and its distribution but also provides rather rapid reaction rate. Effects of different solvents on polymerization of AN were also investigated. The rate of the polymerization in DMF is faster than that in propylene carbonate and toluene. The molecular weight of polyacrylonitrile agrees reasonably well with the theoretical molecular weight in DMF. The rate of polymerization increases with increasing the polymerization temperature, and the apparent activation energy was calculated to be 64.8 kJ mol^?1. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 32–36, 2006     

Thermosensitive copolymer synthesized by controlled living radical polymerization: Phase behavior of diblock copolymers of poly(N‐isopropyl acrylamide) families

In this study, we prepared a series of thermosensitive polymers with low polydispersity index (PDI) values by nitroxide‐mediated controlled radical polymerization (NMRP) with 2,2,6,6‐tetramethyl‐1‐piperdinyloxy nitroxide (TEMPO) as a stable nitroxide‐free radical. Poly(N‐isopropyl acrylamide) (PNIPAAm)‐block‐poly(N‐tert‐butyl acrylamide) (PNTBA) was successfully synthesized, first, through polymerization with N‐isopropyl acrylamide to obtain the reactive polymer PNIPAAm‐TEMPO and, second, through polymerization by the addition of N‐tert‐butyl acrylamide (NTBA). The added molar fraction of NTBA during the second polymerization was adjusted accordingly to obtain the final polymerization product, a thermosensitive polymer (PNIPAAm‐block‐PNTBA), which had a targeted lower critical solution temperature (LCST). The result shows that the synthesis method used in this study effectively controlled the formation of the polymer to obtain a low PDI. The thermosensitive block copolymer, PNIPAAm‐b‐PNTBA (molar ratio = 9:1), with LCSTs in the range 27.7–39.8°C, was obtained through controlled living radical polymerization with PNIPAAm–TEMPO. Specifically, the 5 wt % aqueous solution of PNIPAAm‐b‐PNTBA (molar ratio = 9:1) had an LCST of 37.4°C; this was close to body temperature, 37°C. The 5 wt % aqueous solution of PNIPAAm‐b‐PNTBA (molar ratio = 9:1) showed potential for use in biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43224.     

The influence of polymerization conditions on the tacticity of poly(N-vinyl-2-pyrrolidone)

The tacticities of polyvinylpyrrolidones prepared under various free radical polymerization conditions have been examined by ¹³C n.m.r. at both 25 and 75 MHz. The spectra reveal, contrary to previous reports, that the polymerization solvent influences polymer structure to a small extent. Polymers prepared in water are slightly more syndiotactic than those prepared in organic solvents or in bulk. This difference is attributed to the influence of hydrogen bonding.