Synthesis of poly(methyl methacrylate‐g‐glycidyl azide) graft copolymers using N,N‐dithiocarbamate‐mediated iniferters

A glycidyl azide polymer with pendent N, N‐diethyl dithiocarbamate groups (GAP‐DDC) was prepared by the reaction of poly(epichlorohydrin) (PECH) with pendent N, N‐diethyl dithiocarbamate groups (PECH‐DDC) and sodium azide (NaN₃) in dimethylformamide (DMF). It was then used as a macro‐photoinitiator for the graft polymerization of methyl methacrylate (MMA). Photopolymerization was carried out in a photochemical reactor at a wavelength greater than 300 nm. Conversion was determined gravimetrically and first‐order time conversion plot for the polymerization system showed linear increase with the polymerization time indicating that polymerization proceed in controlled fashion. The molecular weight distribution (M_w/M_n) was in the range of 1.4–1.6 during polymerization. The formation of poly(methyl methacrylate‐g‐glycidyl azide) (PMMA‐g‐GAP) graft copolymer was characterized by gel permeation chromatography, FT‐IR spectroscopy, Thermogravimetric analysis, and differential scanning calorimetry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of poly(epichlorohydrin‐g‐methyl methacrylate) graft copolymers by the combination of cationic and atom transfer radical polymerization

Poly(epichlorohydrin) possessing chloromethyl side groups in the main chain was used in the atom transfer radical polymerization of methyl methacrylate and styrene to yield poly(epichlorohydrin‐g‐methyl methacrylate) and poly(epichlorohydrin‐g‐styrene graft copolymers. The polymers were characterized by ¹H NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, and fractional precipitation method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2725–2729, 2006     

Controlled radical polymerization of styrene initiated by diethyldithiocarbamate‐mediated iniferters

We demonstrated that density functional theory calculations provide a prediction of the trends in C‐S bond dissociation energies and atomic spin densities for radicals using two model compounds as diethyldithiocarbamate (DC)‐mediated iniferters. On the basis of this information, we synthesized 2‐(N,N‐diethyldithiocarbamyl)isobutylic acid (DTCA) and (4‐cyano‐4‐diethyldithiocarbamyl)pentanoic acid (CDPA) as DC‐mediated iniferters. Free‐radical polymerizations of styrene (St) were carried out in benzene initiated by DTCA or CDPA under UV irradiation. The first‐order time‐conversion plots showed the straight line for the UV irradiation system initiated by CDPA indicating the first order in monomer. The number‐average molecular weight (M_n) of the polystyrene (PSt) increased in direct proportion to monomer conversion. The molecular weight distribution (M_w/M_n) of the PSt was in the range of 1.3–1.7. It was concluded this polymerization system proceeded with a controlled radical mechanism. However, photopolymerization of styrene initiated by DTCA showed nonliving polymerization consistent with UV initiation. Theoretical predictions supported these experimental results. Methacrylic acid (MA) could also be polymerized in a living fashion with such a PSt precursor as a macroinitiator because PSt exhibited a DC group at its terminal end. This system could be applied to the architecture of block copolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 413–418, 2005     

Synthesis of poly(epichlorohydrin‐g‐methyl methacrylate) and poly(epichlorohydrin‐g‐styrene) graft copolymers by a combination of cationic and photopolymerization methods

Poly(epichlorohydrin‐g‐styrene) and poly (epichlorohydrin‐g‐methyl methacrylate) graft copolymers were synthesized by a combination of cationic and photoinitiated free‐radical polymerization. For this purpose, first, epichlorohydrin was polymerized with tetrafluoroboric acid (HBF₄) via a cationic ring‐opening mechanism, and, then, polyepichlorohydrin (PECH) was reacted ethyl‐hydroxymethyl dithio sodium carbamate to obtain a macrophotoinitiator. PECH, possessing photolabile thiuram disulfide groups, was used in the photoinduced polymerization of styrene or methyl methacrylate to yield the graft copolymers. The graft copolymers were characterized by ¹H‐NMR spectroscopy, differential scanning calorimetry, and gel permeation chromatography. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of poly(aryl ether sulfone)‐graft‐polystyrene and poly(aryl ether sulfone)‐graft‐[polystyrene‐block‐poly(methyl methacrylate)] through atom transfer radical polymerization

A new graft copolymers poly(aryl ether sulfone)‐graft‐polystyrene (PSF‐g‐PS) and poly(aryl ether sulfone)‐graft‐[polystyrene‐block‐poly(methyl methacrylate)] (PSF‐g‐(PS‐b‐PMMA)) were successfully prepared via atom transfer radical polymerisation (ATRP) catalyzed by FeCl₂/isophthalic acid in N,N‐dimethyl formamide. The products were characterized by GPC, DSC, IR, TGA and NMR. The characterization data indicated that the graft copolymerization was accomplished via conventional ATRP mechanism. The effect of chloride content of the macroinitiator on the graft copolymerization was investigated. Only one glass transition temperature (T_g) was detected by DSC for the graft copolymer PSF‐g‐PS and two glass transition temperatures were observed in the DSC curve of PSF‐g‐(PS‐b‐PMMA). The presence of PSF in PSF‐b‐PS or PSF‐g‐(PS‐b‐PMMA) was found to improve thermal stabilities. © 2002 Society of Chemical Industry     

Photo‐induced controlled radical polymerization of methyl methacrylate mediated by photosensitive nitroxides

Photosensitive nitroxides bearing different chromophore groups (benzophenone, naphthalene and quinoline) were synthesized and characterized. The photochemical properties of the synthesized products were investigated by UV?visible and fluorescence measurements. The results indicated that an efficient energy transfer from the chromophore moiety to the nitroxide radical moiety could occur within the molecular distances. The photo‐induced nitroxide‐mediated polymerization of methyl methacrylate (MMA) was performed using the photosensitive nitroxide/2,2‐dimethoxy‐2‐phenyl acetophenone as a bimolecular mediated system. The controlled character of the polymerization was confirmed by the linear tendency of molecular weight evolution with narrow molecular weight distribution (1.3?1.4). The experimental conditions, such as type of chromophore, initiator concentration and molar ratio of initiator/nitroxide, are discussed for a better understanding of the mechanism of the controlled polymerization. Using the polymerization products as macroinitiator, the chain extension reaction of MMA turned out to be able to re‐initiate further polymerization of the monomer. © 2014 Society of Chemical Industry     

Natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) blends

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber using potassium persulfate as an initiator was carried out by emulsion polymerization. The rubber macroradicals reacted with MMA to form graft copolymers. The morphology of grafted natural rubber (GNR) was determined by transmission electron microscopy and it was confirmed that the graft copolymerization was a surface‐controlled process. The effects of the initiator concentration, reaction temperature, monomer concentration, and reaction time on the monomer conversion and grafting efficiency were investigated. The grafting efficiency of the GNR was determined by a solvent‐extraction technique. The natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) (NR‐g‐MMA/PMMA) blends were prepared by a melt‐mixing system. The mechanical properties and the fracture behavior of GNR/PMMA blends were evaluated as a function of the graft copolymer composition and the blend ratio. The tensile strength, tear strength, and hardness increased with an increase in PMMA content. The tensile fracture surface examined by scanning electron microscopy disclosed that the graft copolymer acted as an interfacial agent and gave a good adhesion between the two phases of the compatibilized blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 428–439, 2001     

Rheological,thermal, and curing properties of natural rubber‐g‐poly(methyl methacrylate)

Graft copolymers of NR and PMMA (i.e., NR‐g‐PMMA) were prepared with the bipolar redox initiation system, using various percentages of molar ratios of NR/MMA at 95/5, 90/10, 80/20, 70/30, and 60/40. It was found that the Mooney viscosity, shear stress, and shear viscosity of the NR‐g‐PMMA increased with an increase in the molar ratio of MMA used in the graft copolymerization. This may be attributed to an increasing trend of the chemical interaction between polar functional groups within the grafted PMMA molecules. Furthermore, a decreasing trend of storage moduli was observed with increasing molar ratios of MMA. The glass transition temperature was obtained from the tan δ curves. We found a slightly increasing trend of the T_g's with an increase in molar ratios of MMA used in the grafting reaction. The NR‐g‐PMMA was later compounded using TBBS as an accelerator. With an increase in molar ratios of MMA in the grafting reaction, we observed an increasing trend of minimum torque, maximum torque, cure time, and scorch time, but quite similar levels of torque difference and crosslink density. Furthermore, the tensile strength of the NR‐g‐PMMA gum vulcanizate increased with an increase in molar ratios of MMA, whereas the elongation at break decreased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1600–1614, 2006     

Synthesis of amphiphilic poly(methyl methacrylate)‐block‐poly(methacrylic acid) diblock copolymers by atom transfer radical polymerization

Atom transfer radical polymerization (ATRP) of 1‐(butoxy)ethyl methacrylate (BEMA) was carried out using CuBr/2,2′‐bipyridyl complex as catalyst and 2‐bromo‐2‐methyl‐propionic acid ester as initiator. The number average molecular weight of the obtained polymers increased with monomer conversion, and molecular weight distributions were unimodal throughout the reaction and shifted toward higher molecular weights. Using poly(methyl methacrylate) (PMMA) with a bromine atom at the chain end, which was prepared by ATRP, as the macro‐initiator, a diblock copolymer PMMA‐block‐poly [1‐(butoxy)ethyl methacrylate] (PMMA‐b‐PBEMA) has been synthesized by means of ATRP of BEMA. The amphiphilic diblock copolymer PMMA‐block‐poly(methacrylic acid) can be further obtained very easily by hydrolysis of PMMA‐b‐PBEMA under mild acidic conditions. The molecular weight and the structure of the above‐mentioned polymers were characterized with gel permeation chromatography, infrared spectroscopy and nuclear magnetic resonance. Copyright © 2005 Society of Chemical Industry     

The inverse emulsion polymerization of acrylamide using poly(methyl methacrylate)‐graft‐polyoxyethylene as the stabilizer

Inverse emulsion polymerization of an aqueous solution of acrylamide (AM) in toluene is carried out using poly(methyl methacrylate)‐graft‐polyoxyethylene (PMMA‐g‐PEO) as an emulsifier. The kinetics of polymerization, morphology of the particle, and particle size of the inverse emulsion have been investigated. The rates of polymerization are found to be proportional to the initiator concentration, the monomer concentration, and the emulsifier concentration. The morphology of particles shows a spherical structure. The mechanism of inverse emulsion polymerization using amphipathic graft copolymer as the emulsifier is proposed. The resulting molecular weights of polyacrylamide are extremely high, and relate to the amphipathic graft copolymer structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 528–534, 2001     

Effect of in situ polymerization conditions of methyl methacrylate on the structural and morphological properties of poly(methyl methacrylate)/poly(acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene)‐g‐styrene) PMMA/AES Blends

In this study, the structural and morphological properties of poly(methyl methacrylate)/poly(acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene‐g‐styrene) (PMMA‐AES) blends were investigated with emphasis on the influence of the in situ polymerization conditions of methyl methacrylate. PMMA‐AES blends were obtained by in situ polymerization, varying the solvent (chloroform or toluene) and polymerization conditions: method A—no stirring and air atmosphere; method B—stirring and N₂ atmosphere. The blends were characterized by infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). The results showed that the PMMA‐AES blends are immiscible and present complex morphologies. This morphology shows an elastomeric dispersed phase in a glassy matrix, with inclusion of the matrix in the elastomer domains, suggesting core shell or salami morphology. The occlusion of the glassy phase within the elastomeric domains can be due to the formation of graft copolymer and/or phase inversion during polymerization. However, this morphology is affected by the polymerization conditions (stirring and air or N₂ atmosphere) and by the solvent used. The selective extraction of the blends' components and infrared spectroscopy showed that crosslinked and/or grafting reactions occur on the elastomer chains during MMA polymerization. The glass transition of the elastomer phase is influenced by morphology, crosslinking, and grafting degree and, therefore, T_g depends on the polymerization conditions. On the other hand, the behavior of T_g of the glassy phase with blend composition suggests miscibility or partial miscibility for the SAN phase of AES and PMMA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation of poly(methyl methacrylate)/titanium oxide composite particles via in‐situ emulsion polymerization

Poly(methyl methacrylate) (PMMA)/Titanium oxide (TiO₂) composite particles were prepared via in‐situ emulsion polymerization of MMA in the presence of TiO₂ particles. Before polymerization, the TiO₂ particles was modified by the silane coupling agent, which is crucial to ensure that PMMA reacts with TiO₂ via covalent bond bindings. The structure of the obtained PMMA/TiO₂ composite particles was characterized using Fourier transform infrared spectra (FTIR) and thermogravimetric analysis (TGA). The results indicate that there are covalent bond bindings between PMMA macromolecules and TiO₂ particles. Based on these facts, several factors affecting the resulting PMMA/TiO₂ composite system, such as the type of coupling agents, the mass ratio of the MMA to the modified TiO₂, the emulsifier concentration, and the initiator concentration, etc., were examined by the measurement of conversion of monomers, the gel content of polymers, the percentage of grafting, and the grafting efficiency, using gravity method or TGA method. As a result, the optimized recipe was achieved, and the percentage of grafting and the grafting efficiency could reach 216.86 and 96.64%, respectively. In addition, the obtained PMMA/TiO₂ composite particles were found to a stable colloidal dispersion in good solvent for PMMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4056–4063, 2006     

Synthesis of poly(methyl methacrylate)-silica nanocomposites using methacrylate-functionalized silica nanoparticles and RAFT polymerization

Well-defined poly(methyl methacrylate)-silica nanocomposites were produced by “grafting through” using reversible addition-fragmentation chain transfer (RAFT) polymerization. The surface of silica nanoparticle was modified covalently by attaching methacryl group to the surface using 3-methacryloxypropyldimethylchlorosilane. Polymerization of methyl methacrylate (MMA) using the 4-cyano-4-(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid RAFT agent, produced the PMMA-SiO₂ nanocomposites. Characterization of these well-defined nanocomposites included FT-IR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), transmission electron microscopy (TEM) and dynamic mechanical analysis. These results show that the T_g values are higher and the mechanical strength of the PMMA-SiO₂ nanocomposites is slightly improved when compared to bulk PMMA. Further, the molecular weight of the PMMA (up to M_n = 100,000) is controlled and the SiO₂ are well dispersed in the PMMA matrix.     

Effects of reaction conditions on poly(methyl methacrylate) polymerized by living radical polymerization with iniferter

Living radical polymerization of methyl methacrylate (MMA) through the use of benzyl diethyl dithiocarbamate (BDC) was studied. The aim was to investigate the role of the concentration, BDC‐to‐MMA mol ratio, and reaction time upon the molecular weight, polydispersity, and conversion of the product. It was found that the molecular weight and the conversion increase with increase of the concentration at the expense of low polydispersity. The reaction time also played a significant role, especially at a relatively long reaction time where molecular weight, polydispersity, and conversion increased with increasing reaction time. In terms of the mol ratio effect, it was found that there was a critical mol ratio for maximum conversion. The results indicate that the kinetics of polymerization of MMA through the use of a BDC inifeter is different from that in the presence of a conventional initiator. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 938–944, 2000     

Atom transfer radical polymerization synthesis and association properties of amphiphilic pullulan copolymers grafted with poly(methyl methacrylate)

Amphiphilic copolymers of pullulan grafted with poly(methyl methacrylate) (PMMA) were synthesized by atom transfer radical polymerization under homogeneous mild conditions without using protecting group chemistry. The hydroxyl groups of pullulan were reacted with 2‐bromoisobutyryl bromide to prepare pullulan macroinitiators with various degrees of substitution. Kinetic study showed that the polymerization was first order. The copolymers were characterized using ¹H NMR spectroscopy and gel permeation chromatography. The molecular weights of the grafted chains were controlled and polydispersities were low. Association properties in aqueous solution were studied using ¹H NMR spectroscopy, dynamic light scattering and transmission electron microscopy. Spherical nanoparticles with size and size distribution significantly affected by the number and length of the grafted chains were formed. Graft copolymers with a degree of substitution of 5.3% and length of PMMA grafted chains from 5 to 35 repeating units formed well‐defined quite monodisperse spherical nanoparticles with hydrodynamic diameters in the range 20–40 nm. This means that nanoparticle size can be tuned by changing the length of the grafted chains for this degree of substitution. Less control of aggregate size was obtained for a degree of substitution of 1.0%. Copyright © 2010 Society of Chemical Industry     

Synthesis and properties of polycarbonate‐poly(methyl methacrylate) graft copolymers by polycondensation of macromonomers

Polycarbonates (PCs) having poly(methyl methacrylate)s (PMMAs) as graft chains were prepared by the polycondensation of PC oligomers bearing chloroformate groups as the end groups with dicarboxyl‐terminated PMMA macromonomers, which were prepared by the radical polymerization of methyl methacrylate in the presence of thiomalic acid as a chain transfer. The resulting PC‐PMMA graft copolymers were transparent in comparison with PC/PMMA blend polymers, and had higher Vickers hardness than blend polymers when both of them had the same PMMA content. According to the results of multiple regression analysis, the improvement of Vickers hardness was conducive to length (46%) and number (37%) of PMMA branches. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2670–2675, 2001     

Controlled radical polymerization of N‐isopropylacrylamide initiated by photofunctional 2‐(N,N‐diethyldithiocarbamyl)isobutyric acid sodium salt in aqueous medium

Photopolymerizations of N‐isopropylacrylamide (NIPAAm) were carried out in water, initiated by 2‐(N,N‐diethyldithiocarbamyl)isobutyric acid sodium salt (DTCA‐Na) as water‐soluble initiator under UV irradiation. The first‐order time‐conversion plots showed slowly decreasing slopes indicating a slow decrease of the active radical concentration. The number‐average molecular weight (M_n) of the obtained poly(N‐isopropylacrylamide) (PNIPAAm) increased in direct proportion, roughly, to monomer conversion. Until ca. 60% of conversion, the polydispersity was relatively narrow (ca. 1.6). 1‐Vinyl‐2‐pyrrolidone (VP) could also be polymerized in living fashion with such PNIPAAm precursor as a macroinitiator, because PNIPAAm exhibited dithiocarbamate (DC) groups at terminal ends. It was concluded that the polymerization of NIPAAm proceeded via a controlled radical mechanism in the range ～60% of conversion. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3233–3238, 2004     

Synthesis of poly(cyclohexene oxide)‐block‐polystyrene by combination of radical‐promoted cationic polymerization,atom transfer radical polymerization and click chemistry

The combination of radical‐promoted cationic polymerization, atom transfer radical polymerization (ATRP) and click chemistry was employed for the efficient preparation of poly(cyclohexene oxide)‐block‐polystyrene (PCHO‐b‐PSt). Alkyne end‐functionalized poly(cyclohexene oxide) (PCHO‐alkyne) was prepared by radical‐promoted cationic polymerization of cyclohexene oxide monomer in the presence of 1,2‐diphenyl‐2‐(2‐propynyloxy)‐1‐ethanone (B‐alkyne) and an onium salt, namely 1‐ethoxy‐2‐methylpyridinium hexafluorophosphate, as the initiating system. The B‐alkyne compound was synthesized using benzoin photoinitiator and propargyl bromide. Well‐defined bromine‐terminated polystyrene (PSt‐Br) was prepared by ATRP using 2‐oxo‐1,2‐diphenylethyl‐2‐bromopropanoate as initiator. Subsequently, the bromine chain end of PSt‐Br was converted to an azide group to obtain PSt‐N₃ by a simple nucleophilic substitution reaction. Then the coupling reaction between the azide end group in PSt‐N₃ and PCHO‐alkyne was performed with Cu(I) catalysis in order to obtain the PCHO‐b‐PSt block copolymer. The structures of all polymers were determined. Copyright © 2010 Society of Chemical Industry     

Synthesis,characterization, and mechanical property of poly(urethane‐glycidyl methacrylate‐methyl methacrylate) hybrid polymers

Hybrid particles of polyurethane (PU) containing a number of small poly(methyl methacrylate) (PMMA) nanoparticles inside were prepared using glycidyl methacrylate (GMA) monomer as a linker between PU and PMMA; the resulting polymers were poly (urethane‐glycidyl methacrylate‐methyl methacrylate) (PUGM). It was found that the average particle size (D_p) of the PU particles decreased by the inclusion of PMMA particles possibly owing to the low‐solution viscosity of PU. However, D_p of the PUGM hybrid particles increased with increasing the number of covalent bonds between PMMA and PU, which might be due to decreasing the amount of ionic groups per PU chain. Subsequently, the tensile properties of the films made of the PUGM hybrid particles were investigated. It was observed that the modulus of the PU films increased upon the addition of PMMA particle because of a filler effect. In addition, it was seen that the modulus of PUGM hybrid films increased further with increasing the number of covalent bonds. This was attributed to “restricted mobility” of PU chains anchored to the PMMA particles. It was also observed that the tensile strength changed only slightly for PUGM particles, suggesting that the PU matrix was probably responsible for the necking behavior of the films. The elongation of the samples was found to depend on both the presence of covalent bonds between the PMMA particles and PU matrix and the reduced mobility of the PU chains anchored to PMMA particles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Photocationic and radical polymerizations by novel N‐phenacylammonium salts

Novel N‐phenacylammonium salts [N‐(α‐benzoylbenzyl)‐, N‐(1‐benzoylethyl)‐, N‐phenacyl‐, pyrazinium, 3‐bromoquinolinium, benzothiazolium, or p‐cyanopyridinium hexafluoroantimonates] were synthesized by the reaction of α‐benzoylbenzyl bromide, 2‐bromopropiophenone or phenacylbromide, and the corresponding N‐hetero aromatic compound, followed by anion exchange with KSbF₆. These N‐phenacylammonium salts showed higher activity than previously reported N‐benzyl‐2‐cyanopyridinium hexafluoroantimonate in the photopolymerization of epoxides. Further, these N‐phenacylammonium salts served as photoradical and thermal cationic initiators as well as photocationic initiators. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3470–3476, 2004