Graft copolymerization of methyl methacrylate with an N‐substituted maleimide–liquid‐crystalline copolymer by atom transfer radical polymerization

The synthesis of novel copolymers consisting of a side‐group liquid‐crystalline backbone and poly (methyl methacrylate) grafts were realized by the use of atom transfer radical polymerization (ATRP). In the first stage, the bromine‐functional copolymers 6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate and (2,5‐dioxo‐2,5‐dihydro‐1H‐pyrrole‐1‐yl)methyl 2‐bromopropanoate were synthesized by free‐radical polymerization. These copolymers were used as initiators in the ATRP of methyl methacrylate to yield graft copolymers. Both the macroinitiator and graft copolymers were characterized by ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. The ATRP graft copolymerization was supported by an increase in the molecular weight of the graft copolymers compared to that of the macroinitiator and also by their monomodal molecular weight distribution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of cyclohexanone formaldehyde resin‐methylmethacrylate block‐graft copolymers via ATRP

Well defined block‐graft copolymers of cyclohexanone‐formaldehyde resin (CFR) and methylmethacrylate (MMA) were prepared via atom transfer radical polymerization (ATRP). In the first step, cyclohexanone formaldehyde resin (CFR) containing hydroxyl groups were modified with 2‐bromopropionyl bromide. Resulting multifunctional macroinitiator was used in the ATRP of MMA using copper bromide (CuBr) and N,N,N′,N″,N″‐pentamethyl‐diethylenetriamine (PMDETA) as catalyst system at 90°C. The chemical composition and structure of the copolymers were characterized by nuclear magnetic resonance (¹H‐NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and molecular weight measurement. Molecular weight distributions of the CFR graft copolymers were measured by gel permeation chromatography (GPC). M_n values up to 19,000 associated with narrow molecular weight distributions (polydispersity index (PDI) < 1.6) were obtained with conversions up to 49%. Coating properties of synthesized graft copolymers such as adhesion and gloss values were measured. They exhibited good adhesion properties on Plexiglas substrate. The thermal behaviors of all polymers were conducted using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Graft copolymers and high‐molecular‐weight star‐like polymers by atom transfer radical polymerization

Grafting of tert‐butyl acrylate (tBuA), methyl methacrylate (MMA), and styrene (St) monomers (M) by Cu(I)‐mediated ATRP from polystyrene (PSt) macroinitiator (M_n = 5620, polydispersity index, PDI = 1.12), containing initiating 2‐bromopropionyloxy groups (I) (bound to 34% of aromatic cores; 11 groups per backbone), was performed using conditions suitable for the respective homopolymerizations. The preparation of PSt‐g‐PtBuA in bulk using an initial molar ratio [M]₀/[I]₀ = 140 had a controlled character up to M_n = (132–148) × 10³ (PDI = 1.08–1.16). With MMA and St and using the same [M]₀/[I]₀, preliminary experiments were made; the higher the monomer conversion, the broader was the distribution of molecular weight of the products. Graft copolymerizations of all these monomers at [M]₀/[I]₀ = 840 or 1680 were successfully conducted up to high conversions. Low‐polydispersity copolymers, with very long side chains, in fact star‐like copolymers, were obtained mainly by tuning the deactivator amount in the reaction mixture. (PSt‐g‐PtBuA, DP_n,sc (DP of side chain) = 665, PDI = 1.24; PSt‐g‐PMMA, DP_n,sc = 670, PDI = 1.43; PSt‐g‐PSt, DP_n,sc = 324, PDI = 1.11). Total suppression of intermolecular coupling was achieved here. However, the low concentrations of initiator required long reaction times, leading sometimes to formation of a small amount (～5%) of low‐molecular‐weight polymer fraction. This concomitant process is discussed, and some measures for its prevention are proposed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3662–3672, 2006     

Graft copolymerization of N‐vinyl‐2‐pyrrolidone onto sodium carboxymethylcellulose with azobisisobutyronitrile as the initiator

Graft copolymers of sodium carboxymethylcellulose with N‐vinyl‐2‐pyrrolidone were prepared in aqueous solutions with azobisisobutyronitrile as the initiator. The graft copolymers [sodium carboxymethylcellulose‐g‐poly(N‐vinyl‐2‐pyrrolidone)] were characterized with Fourier transform infrared spectroscopy, elemental analysis, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and scanning electron microscopy. The grafting parameters, including the graft yield of the graft copolymer and the grafting efficiency of the reaction, were evaluated comparatively. The effects of reaction variables such as the time, temperature, and monomer and initiator concentrations on these parameters were studied. The graft yield and grafting efficiency increased and then decreased with increasing concentrations of N‐vinyl‐2‐pyrrolidone and azobisisobutyronitrile and increasing polymerization temperatures. The optimum temperature and polymerization time were 70°C and 4.30 h, respectively. Further changes in the properties of grafted sodium carboxymethylcellulose, such as the intrinsic viscosity, were determined. The overall activation energy for the grafting was also calculated to be 10.5 kcal/mol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 936–943, 2007     

Reactivity ratios of free monomers and their charge‐transfer complex in the copolymerization of N‐butyl maleimide and styrene

As for the charge‐transfer complex (CTC) formed by N‐butyl maleimide (NMBI) and styrene in chloroform, the complex formation constant was determined by ¹H‐NMR of Hanna–Ashbaugh. The copolymerization of NBMI (NBMI, M₁) and styrene (St, M₂) in chloroform using AIBN as an initiator was investigated. On the basis of the kinetic model proposed by Shan, the reactivity ratios of free monomers and CTC in the copolymerization were calculated to be r₁₂ = 0.0440, r₂₁ = 0.0349, r_1C = 0.00688, r_2C = 0.00476, and the ratios of rate constants were obtained to be k_1C/k₁₂ = 6.40, k_2C/k₂₁ = 7.33. In addition, the copolymer was characterized by IR, ¹H‐NMR, DSC, and TGA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3007–3012, 2002; DOI 10.1002/app.2330     

Novel polymerizable N‐aromatic maleimides as free radical initiators for photopolymerization

Four kinds of polymerizable N‐aromatic maleimides (MIs)—4‐[(4‐maleimido)phenoxy]benzophenone (MPBP), 4,4′‐bis[(4‐maleimido)phenoxy]benzophenone (BMPBP), 4‐maleimidobenzophenone (MBP), and 4,4′‐bismaleimidobenzophenone (BMBP)—were synthesized as free radical photoinitiators, by introducing directly N‐phenylmaleimide groups or maleimide groups into the molecule of benzophenone (BP). Compared with BP, their UV‐visible spectra have a significantly red‐shifted maximum absorption. The maximum absorption of MIs containing bifunctional maleimide groups is slightly larger than the corresponding monofunctional ones. Choosing an unsaturated tertiary amine N,N‐dimethylaminoethyl methacrylate (DMAEMA) as coinitiator, the photopolymerization of 1,6‐hexanediol diacrylate (HDDA), initiated by these four MIs, was studied through photo‐DSC. The results show that all the MIs are dramatically more efficient than BP. Among them, MPBP is the most efficient, in which the polymerization rate is almost three times as high as that of the BP system. Photoinitiators containing bifunctional maleimide groups, though having higher final conversion, are less efficient than the corresponding monofunctional ones. These polymerizable photoredox systems significantly reduced the migration of the active species, leading to their higher efficiency. Copyright © 2006 Society of Chemical Industry     

Graft copolymerization of styrene and acrylonitrile onto EPDM

Acrylonitrile–EPDM–styrene (AES) graft copolymers were synthesized by solution graft polymerization of styrene (St) and acrylonitrile (AN) onto EPDM in an n‐hexane/benzene solvent with benzoyl peroxide (BPO) as an initiator. The structure changes were studied by an FTIR spectrophotometer. The grafting parameters were calculated gravimetrically. The influence of the polymerization conditions, such as the reaction time, concentration of the initiator, EPDM content, and weight ratio of St/AN, on the structure of the products was investigated. It was found that a proper initiator concentration and EPDM content will give a high grafting ratio of the AES resin. The thermal property of the copolymer was studied using programmed thermogravimetric analysis (TGA). The results showed that the copolymer has a better heat‐resistant property than that of ABS, especially for the initial decomposition temperature (T_in) and the maximum weight loss rate temperature (T_max). Also, the mechanism of the graft reaction was discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 428–432, 2002     

Poly(N‐hydroxyethyl acrylamide)‐b‐polystyrene by combination of ATRP and aminolysis processes

Block copolymers of very hydrophilic poly(N‐hydroxyethyl acrylamide) (PHEAA) with polystyrene (PS) were successfully synthesized by sequential atom transfer radical polymerization of ethyl acrylate (EA) and styrene monomers and subsequent aminolysis of the acrylic block with ethanolamine. Quantitative aminolysis of poly(ethyl acrylate) (PEA) block yielded poly(N‐hydroxyethyl acrylamide)‐b‐polystyrene in well‐defined structures, as evidenced by Fourier transform infrared spectroscopy (FTIR) and ¹H‐NMR spectroscopy techniques. Three copolymers with constant chain length of PHEAA (degree of polymerization: 80) and PS blocks with 21, 74, and 121 repeating units were prepared by this method. Among those, the block copolymer with 21 styrene repeating units showed excellent micellation behavior in water without phase inversion below 100°C, as inferred from dynamical light scattering, environmental scanning electron microscopy, and fluorescence measurements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Toughening of cyanate ester resin by N‐phenylmaleimide–N‐(p‐hydroxy)phenyl‐maleimide–styrene terpolymers and their hybrid modifiers

N‐Phenylmaleimide–N‐(p‐hydroxy)phenylmaleimide–styrene terpolymer (HPMS), carrying reactive p‐hydroxyphenyl groups, was prepared and used to improve the toughness of cyanate ester resins. Hybrid modifiers composed of N‐phenylmaleimide–styrene copolymer (PMS) and HPMS were also examined for further improvement in toughness. Balanced properties of the modified resins were obtained by using the hybrid modifiers. The morphology of the modified resins depends on HPMS structure, molecular weight and content, and hybrid modifier compositions. The most effective modification of the cyanate ester resin was attained because of the co‐continuous phase structure of the modified resin. Inclusion of the modifier composed of 10 wt% PMS (M_w 136 000 g mol^?1) and 2.5 wt% HPMS (hydroxyphenyl unit 3 mol%, M_w 15 500 g mol^?1) led to 135% increase in the fracture toughness (K_IC) for the modified resin with a slight loss of flexural strength and retention of flexural modulus and glass transition temperature, compared with the values for the unmodified resin. Furthermore, the effect of the curing conditions on the mechanical and thermal properties of the modified resins was examined. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified cyanate ester resin system. © 2001 Society of Chemical Industry     

Synthesis of methyl methacrylate and N‐aryl itaconimide block copolymers via atom‐transfer radical polymerization

The paper describes the synthesis of block copolymers of methyl methacrylate (MMA) and N‐aryl itaconimides using atom‐transfer radical polymerization (ATRP) via a poly(methyl methacrylate)–Cl/CuBr/bipyridine initiating system or a reverse ATRP AIBN/FeCl₃·6H₂O/PPh₃ initiating system. Poly(methyl methacrylate) (PMMA) macroinitiator, ie with a chlorine chain‐end (PMMA‐Cl), having a predetermined molecular weight (M_n = 1.27 × 10⁴ g mol^?1) and narrow polydispersity index (PDI = 1.29) was prepared using AIBN/FeCl₃·6H₂O/PPh₃, which was then used to polymerize N‐aryl itaconimides. Increase in molecular weight with little effect on polydispersity was observed on polymerization of N‐aryl itaconimides using the PMMA‐Cl/CuBr/Bpy initiating system. Only oligomeric blocks of N‐aryl itaconimides could be incorporated in the PMMA backbone. High molecular weight copolymer with a narrow PDI (1.43) could be prepared using tosyl chloride (TsCl) as an initiator and CuBr/bipyridine as catalyst when a mixture of MMA and N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 was used. Thermal characterization was performed using differential scanning calorimetry (DSC) and dynamic thermogravimetry. DSC traces of the block copolymers showed two shifts in base‐line in some of the block copolymers; the first transition corresponds to the glass transition temperature of PMMA and second transition corresponds to the glass transition temperature of poly(N‐aryl itaconimides). A copolymer obtained by taking a mixture of monomers ie MMA:N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 showed a single glass transition temperature. Copyright © 2005 Society of Chemical Industry     

Homopolymerization and copolymerization of N‐substituted maleimides with chiral anionic initiators

Novel optically active anionic initiators bearing a chiral oxazole substituent on the fluorene ring, (S)‐1‐(9H‐fluoren‐2‐yl)‐4‐isopropyl‐4,5‐dihydrooxazole lithium (Li‐(S)‐1‐FIDH) and (S)‐2‐(9H‐fluoren‐2‐yl)‐4‐isopropyl‐4,5‐dihydrooxazole lithium (Li‐(S)‐2‐FIDH), were prepared. Anionic homopolymerizations of achiral N‐substituted maleimide (RMI) with the chiral initiators were investigated. The optically active polymers obtained were attributed to asymmetric induction of the chiral initiators. The very crowded chiral initiator Li‐(S)‐1‐FIDH was found to play a better asymmetric induction role in the polymers than Li‐(S)‐2‐FIDH. Anionic copolymerization of (R)‐(+)‐N‐1‐phenylethyl maleimide and optically inactive RMI with Li‐(S)‐1‐FIDH were also studied. © 2014 Society of Chemical Industry     

Graft copolymerization of vinyl monomers onto silk fibers initiated by a semiconductor‐based photocatalyst

Graft copolymerization onto silk (Bombyx mori) was carried out with vinyl monomers (methyl methacrylate and acrylamide) and initiated by a semiconductor‐based photocatalyst (cadmium sulfide). The utility of a semiconductor as an initiator in free‐radical photografting and the effects of ethylene glycol and triethylamine with cadmium sulfide on graft copolymerization were explored. Depending on the reaction conditions, 10–48% grafting with methyl methacrylate and 4–26% grafting with acrylamide were achieved. The reaction conditions were optimized, and the grafted fibers were characterized with scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetry analysis, and tensile strength measurements. The chemical resistance and water absorption of the grafted fibers were compared with those ungrafted fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Graft copolymerization of acrylic acid onto methylcellulose by potassium permanganate‐p‐xylene redox pair

Poly(acrylic acid) was grafted onto methylcellulose in aqueous media by a potassium permanganate‐p‐xylene redox pair. Within the concentration range from 0.93 × 10^?3 to 9.33 × 10^?3M, p‐xylene, the graft copolymerization reaction exhibited minimum and maximum graft yields and was associated with two precursor‐initiating species, a p‐xylyl radical and its diradical derivative. The efficiency of the graft was low, not higher than 12.9% at a p‐xylene concentration of 0.93 × 10^?3M and suggested the dominance of a competitive homopolymerization reaction under homogeneous conditions. The effect of permanganate on the graft yield was normal and optimal at 135% graft yield, corresponding to a concentration of the latter of 33.3 × 10^?3M over the range from 8.3 × 10^?3 to 66.7 × 10^?3M. The conversion in graft yield showed a negative dependence on temperature in the range 30–60°C and suggested a preponderance of high activation energy transfer reaction processes. The calculated composite activation energy for the graft copolymerization was 7.6 kcal/mol. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 278–281, 2004     

Thermoresponsive behaviour in aqueous solution of poly(maleic acid‐alt‐vinyl acetate) grafted with poly(N‐isopropylacrylamide)

The synthesis of a thermoresponsive graft copolymer consisting of a maleic acid/vinyl acetate alternating copolymer backbone (MAc‐alt‐VA) and poly(N‐isopropylacrylamide) (PNIPAM) side chains is reported. Turbidimetric measurements in dilute aqueous solutions showed that no macroscopic phase separation takes place when the temperature is raised above the lower critical solution temperature (LCST) of PNIPAM, even at pH = 2. Moreover, in semi‐dilute aqueous solutions, a pronounced thermally induced viscosity increase (thermothickening) was observed. This thermoresponsive behaviour has been attributed to the interconnection of the hydrophilic MAc‐alt‐VA graft copolymer backbones by means of the hydrophobic PNIPAM side chain aggregates formed as the temperature increases above the LCST of this polymer. Copyright © 2004 Society of Chemical Industry     

Synthesis of hydroxyethylcellulose‐graft‐poly(N,N‐dimethylacrylamide) copolymer by ATRP and as dynamic coating in capillary electrophoresis

Hydroxyethylcellulose‐graft‐poly (N, N‐dimethylacrylamide) was synthesized by successive atom transfer radical polymerization (ATRP) of N,N‐dimethylacrylamide (DMA) monomer using HEC‐Br as initiator, CuBr and 5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazamacrocyclotetradecane (Me₆[14]aneN₄) as catalyst and ligand, with molar ratio DMA: HEC‐Br (C? Br): CuBr: Me₆[14]aneN₄ = 100 : 1 : 1 : 3. HEC–Br macroinitiator was synthesized by esterification of HEC with 2‐bromoisobutyryl bromide. GPC and ¹H NMR studies show that the molecular weight of the resulting PDMA increased linearly with the conversion. Within 6 h, the polymerization can reach almost 60% of conversion. The copolymer is applied for the separation of basic proteins in capillary electrophoresis. The results show that this medium has a powerful capability in resisting basic proteins adsorption because the polymer forms noncovalent coating in silica capillaries. With a broad range of pH 2–7, proteins were separated with sufficient efficiencies above 200,000 plates/m. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

ESR and kinetic study of a novel polymerizable photoinitiator comprising the structure of N‐phenylmaleimide and benzophenone for photopolymerization

A novel polymerizable photoinitiator, 4‐[(4‐maleimido)phenoxy]benzophenone (MPBP) comprising the structure of N‐phenylmaleimide and benzophenone was used for the photopolymerization with N,N‐dimethylaminoethyl methacrylate (DMAEMA) as coinitiator. The ESR spectrum of this photoredox system was studied and compared with BP/DMAEMA; the results showed the same signals of them and verified that N‐phenylmaleimide does not generate radicals. The kinetics for photopolymerization of methyl methacrylate (MMA) using such system was studied by dilatometer. It was found that the polymerization rate was proportional to the 0.3172th power of the MPBP concentration, the 0.7669th power and the 0.1765th power of MMA concentration and DMAEMA concentration respectively; the overall apparent activation energy obtained was 31.88 kJ/mol. The polymerization kinetics of 1,6‐hexanediol diacrylate (HDDA) initiated by such system was studied by photo‐DSC. It showed that the increase in the MPBP concentration, light intensity, and temperature leads to increased polymerization rate and final conversion. The apparent activation energy was 11.25 kJ/mol. This polymerizable photoredox system was significantly favorable for reducing the migration of active species but owning high efficiency. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2347–2354, 2006     

High molecular weight hydrophilic functional copolymers by free‐radical copolymerization of acrylamide and of N‐acryloylmorpholine with N‐acryloxysuccinimide: Application to the synthesis of a graft copolymer

Free‐radical solution copolymerization of acrylamide (AAm) and of a disubstituted acrylamide derivative, N‐acryloylmorpholine (NAM), with N‐acryloxysuccinimide (NAS) was investigated with the aim to obtain a copolymer of at least 100,000 g mol^?1. Different polymerization conditions likely to increase the molecular weight were studied such as monomer and initiator concentrations, temperature, and nature of the solvent. The molecular weights were determined by SEC using a light‐scattering detector. The grafting of end‐functionalized polysaccharide chains onto such high molecular weight poly(NAM‐co‐NAS) was performed and a graft copolymer bearing a high number of saccharidic branches was obtained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1808–1816, 2003     

Synthesis of stimuli‐responsive star‐like copolymer H20‐PNIPAm‐r‐PEGMA via the ATRP copolymerization technique and its micellization in aqueous solution

A series of novel star‐like copolymers H20‐poly(N‐isopropylacrylamide)‐random‐poly(poly(ethylene glycol) methyl ether methacrylate) (H20‐PNIPAm‐r‐PEGMA), which could respond to both temperature and ionic strength stimuli in aqueous solution were synthesized by atom transfer radical polymerization. Stimuli‐response of these copolymers in aqueous solution was characterized by dynamic laser scattering (DLS), ¹H‐NMR and turbidity. In aqueous solution, these star‐like copolymers exhibited response to temperature and ionic strength with tunable low‐critical solution temperature (LCST) from 32 to 100°C. The LCST values of copolymers increased with increasing PEGMA contents, while decreased with increasing ionic strength. An interesting phenomenon, which should be a unique character of star‐like copolymer, was observed by the turbidity test of copolymer 1160. The addition of sodium chloride and increase of concentration can let copolymer 1160 behave normally, which was further confirmed by atomic force microscopy and DLS. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Graft copolymerization of styrene onto casein initiated by potassium diperiodatonickelate (IV) in alkaline medium

A novel redox system, potassium diperiodatonickelate (Ni(IV))‐casein is used to initiate graft copolymerization of Styrene onto casein under different conditions in aqueous alkaline solution. Graft copolymers with both high grafting efficiency (>98%) and percentage of grafting(>300%) are obtained, which indicated that (Ni(IV))‐casein redox pair is an efficient initiator for this grafting. The effects of reaction parameters, such as monomer‐to‐casein weight ratio, initiator concentration, pH, time, and temperature, are investigated. A tentative initiation mechanism is proposed. The structures and properties of the graft copolymer are characterized by Fourier transform infrared Spectroscopy, X‐ray diffraction diagrams, and Scanning Electron Microscope. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4247–4251, 2006     

New syntheses of graft copolymers using the DPE-technique: ATRP graft copolymerization

Summary A new one-step synthesis of a set of macroinitiators for atom transfer radical polymerization (ATRP) via controlled radical polymerization is presented. The macroinitiators consist of methacrylate and p-chloromethylstyrene (CMS) and were synthesized by controlled radical polymerization in the presence of l,l-diphenylethylene (DPE) using azobisisobutyronitrile (AIBN) as initiator. The resulting macroinitiators were used for the ATRP of different methacrylates yielding graft copolymers which were characterized by SEC and NMR. Received: 25 July 2002/Revised version: 28 October 2002/ Accepted: 28 October 2002 Correspondence to Oskar Nuyken