New chain transfer agents for free radical polymerizations

The palmitoyl ester of N-hydroxypyridine-2-thione displayed useful chain transfer properties in free radical polymerizations of methyl methacrylate and styrene. Retardation, however, accompanied the lowering of molecular weight in methyl acrylate and vinyl acetate polymerizations. 4-Methyl-3-palmitoyloxythiazol-2(3H)-thione had good chain transfer activity with methyl methacrylate, styrene and methyl acrylate. Although benzyl thionobenzoate exhibited virtually ‘ideal’ behaviour (chain transfer constant C_x ～1) in styrene and methyl acrylate polymerizations, it was ineffective in lowering molecular weight of poly(methyl methacrylate). Severe retardation was observed with vinyl acetate. Addition-fragmentation pathways are postulated for chain transfer.     

Poly(ethylene oxide) macromonomers

Summary Poly(ethylene oxide) macromonoraers (M₂) carrying p-vinylbenzyl or methacryloyl group at the -end and methyl or dodecyl group at the -end were prepared, and radical-copolynerized with benzyl methacrylate or styrene (M₁). Relative reactivities of the macroraonomers (1/r₁), were found to be significantly smaller than those of the corresponding model monomers of low molecular weights in all cases where the macromonomer (M₂) and the homopolymer of the comonomer(poly-M₁), are incompatible, supporting our previous suggestion of a repulsion between M₂ and poly-M₁, radical as a factor for retarding their mutual reaction.     

Bulk and emulsion copolymerizations of n-butyl acrylate and poly(methyl methacrylate) macromonomer

Bulk and emulsion copolymerizations of an ω-unsaturated poly(methyl methacrylate) (PMMA) macromonomer with n-butyl acrylate (n-BA) were investigated. The reactivity of PMMA macromonomer in bulk copolymerization with n-BA was found to be lower than that of methyl methacrylate monomer with n-BA. The incorporation of PMMA macromonomer into poly(butyl acrylate) (PBA) latex particles by miniemulsion copolymerization was proved by high performance liquid chromatography-silica adsorption spectroscopy. Dynamic mechanical studies showed that PMMA macromonomer was grafted to the PBA backbone, and the degree of grafting increased as the ratio of PMMA macromonomer to n-BA increased. Microphase separation of the PMMA macromonomer grafts was observed at higher ratio of macromonomer (higher or equal to 10% weight of macromonomer based on total polymer phase). The n-BA/PMMA macromonomer copolymer behaved completely differently from the physical blend of PBA and PMMA macromonomer particles of the same composition. © 1996 John Wiley & Sons, Inc.     

Thiohydroxamic esters

Summary N-Hydroxypyridine-2-thione derivativesIa-c and N-hydroxy-4-methylthiazole-2(3H)-thione derivativesIIa-b act as chain transfer agents in free radical polymerizations of methyl methacrylate (C _x =0.6–4.3), styrene (C _x =0.32–3.9), methyl acrylate (C _x =3.1–20), and vinyl acetate (C _x =9.7–80) at 60°C. Some retardation occurs with vinyl acetate and methyl acrylate.Ib also has the property of initiating the polymerization of methyl methacrylate photochemically, whileIIb acts as a thermal initiator. The chain transfer constants ofIIb make it particularly suitable for regulating molecular weight in batch polymerizations of methyl methacrylate and styrene.     

Copolymerization of methyl α-(chloromethy1)acrylate with styrene accompanied by addition-fragmentation chain transfer

Summary Copolymerization of methyl α-(chloromethy1)acrylate (MCMA, M₁) as homo-polymerizable addition-fragmentation chain transfer (AFCT) agent with styrene (St, M₂) was investigated. The monomer reactivity ratios were r ₁ = 0.12 and r ₂ = 0.18 at 60° C indicating high alternating tendency. The copolymers bearing the 2-carbomethoxy-2-propenyl (CH₂=C(C0₂Me)CH₂-) ω-end group formed by AFCT were submitted for ¹H-NMR structural analysis. The M _n, of copolymer and contribution of AFCT as end forming reactions decreased and increased with increasing MCMA content in comonomer, respectively. The propenyl end groups bound to the St and MCMA units were separately detected. Furthermore, it was concluded that the MCMA-St copolymerization involves not only AFCT but also chlorine abstraction by the poly(St) radical. Received: 21 October 2002/Accepted: 19 November 2002 Correspondence to Bunichiro Yamada     

Poly(ethylene oxide) macromonomers

Summary p-Vinylbenzyl-terninated poly(ethylene oxide) macromonomers (M₂) were radical-copolymerized with styrene (M₁) in benzene, tetrahydrofuran, and methyl isobutyl ketone at 60°C. Relative reactivity of the macromonomer toward polystyryl radical, as estimated by l/r₁ was found to decrease with increasing number-average degree of polymerization and also in a solvent which gives a higher [] of both polystyrene and the macromonomer. The results support our previous suggestion that a repulsion between the macromonomer and the propagating polymer radical can be a factor responsible for disturbing their mutual reaction.Part 1: Ref. 1, Part 2: Ref. 2     

n‐Butyl acrylate based latex interpenetrating polymer networks used as processing modifiers and impact modifiers of poly(vinyl chloride)

A latex interpenetrating polymer network (LIPN), consisting of poly(n‐butyl acrylate), poly(n‐butyl acrylate‐co‐ethylhexyl acrylate), and poly(methyl methacrylate‐co‐ethyl acrylate) and labeled PBEM, with 1,4‐butanediol diacrylate as a crosslinking agent was synthesized by three‐stage emulsion polymerization. The initial poly(n‐butyl acrylate) latex was agglomerated by a polymer latex containing an acrylic acid residue and then was encapsulated by poly(n‐butyl acrylate‐co‐ethylhexyl acrylate) and poly(methyl methacrylate‐co‐ethyl acrylate). A polyblend of poly(vinyl chloride) (PVC) and PBEM was prepared through the blending of PVC and PBEM. The morphology and properties of the polyblend were studied. The experimental results showed that the processability and impact resistance of PVC could be enhanced considerably by the blending of 6–10 phr PBEM. This three‐stage LIPN PBEM is a promising modifier for manufacturing rigid PVC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1168–1173, 2004     

Atom transfer radical polymerization grafting of highly functionalized polystyrene and poly(4‐methylstyrene) macroinitiators with tert‐butyl acrylate

Two monodisperse graft copolymers, poly(4‐methylstyrene)‐graft‐poly(tert‐butyl acrylate) [number‐average molecular weight (M_n) = 37,500, weight‐average molecular weight/number‐average molecular weight (M_w/M_n) = 1.12] and polystyrene‐graft‐poly(tert‐butyl acrylate) (M_n = 72,800, M_w/M_n = 1.12), were prepared by the atom transfer radical polymerization of tert‐butyl acrylate catalyzed with Cu(I) halides. As macroinitiators, poly{(4‐methylstyrene)‐co‐[(4‐bromomethyl)styrene]} and poly{styrene‐co‐[4‐(1‐(2‐bromopropionyloxy)ethyl)styrene]}, carrying 40% of the bromoalkyl functionalities along the chain, were used. The dependencies of molecular parameters on monomer conversion fulfilled the criteria for controlled polymerizations. In contrast, the dependencies of monomer conversion versus time were nonideal; possible causes were examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2930–2936, 2002     

Use of poly(styrene)-block-poly(ethyleneoxide) as emulsifier in emulsion polymerization

Summary Poly(styrene)-block-poly(ethyleneoxide), abbreviated as (PS-b-PEO) were used as emulsifiers in emulsion polymerization of styrene and methyl methacrylate. The block copolymers had a poly(styrene) block with M_n=1000 g/mol and a poly(ethyleneoxide) block with M_n=1000, 3000 or 5000 g/mol, respectively. Stable dispersions were obtained when the PEO block molecular weight was higher than 1000 g/mol. Also the amphiphilic properties of the copolymers depended on the PEO chain length. Block copolymer micelles with hydrodynamic radii between 11 and 17nm were observed. Emulsion polymerization was performed at different block copolymer concentration at 60 and 80°C. Particle size varied between 50 and 300nm and decreased with increasing copolymer concentration. The particle size was larger at higher temperature, but the size distribution was narrower. Polymerization of methyl methacrylate gave smaller particles when compared to styrene. The dispersions were very stable towards high electrolyte concentration, but flocculation occurred at elevated temperatures. Both observations indicate that the dispersions are sterically stabilized.     

Block copolymer synthesis and chain extension from TEMPO‐terminated chains formed by ultrasonic chain scission

Long poly(ethyl methacrylate) (M_n = 2,300,000) and polystyrene (M_n = 1,200,000) chains were subjected to ultrasonic scission in the presence of a radical scavenger, 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO). This procedure yielded polymers with lower molecular weights and TEMPO terminal units. Application of these polymers in stable radical mediated polymerization of styrene resulted in chain extension and block copolymers, depending on the precursor polymer. Block copolymer formation was evidenced by NMR measurement, and chain extension was shown by GPC analysis. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1950–1953, 2000     

Synthesis,characterization, and thermal behavior study of methyl methacrylate polymers containing 4‐carbazole substitutes

A new polymerizable monomer, [4‐(9‐ethyl)carbazolyl]methyl methacrylate ( 2 ), was synthesized by reacting of methacrylic acid and 4‐hydroxymethyl‐9‐ethyl carbazole ( 1 ) by esterification procedure in the presence of N,N′‐dicyclohexylcarbodiimide. The resulting monomer was then polymerized free‐radically to form the poly(methyl methacrylate) containing 4‐(9‐ethyl)carbazolyl pend ent groups. Also, copolymerization of monomer 2 with various acrylic monomers such as methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, and n‐butyl acrylate by azobisisobutyronitrile as a free radical polymerization initiator gave the related copolymers in high yields. The structure of all the resulted compounds was characterized and confirmed by FTIR and ¹H NMR spectroscopic techniques. The average molecular weight of the obtained polymers was determined by gel permeation chromatography using tetrahydrofurane as the solvent. The thermal gravimetric analysis and differential scanning calorimeter instruments were used for studying of thermal properties of polymers. It was found that, with the incorporation of bulky 4‐(9‐ethyl)carbazolyl substitutes in side chains of methyl methacrylate polymers, thermal stability and glass transition temperature of polymers are increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4989–4995, 2006     

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 pure (Co) polymers via supported cobalt (II)-catalyzed controlled/“living” radical polymerization

Cross-linked polyacrylic resin supported-cobalt (II) catalyst was successfully employed in controlled/“living” radical polymerization of various monomers including n-butyl acrylate (BA), ethyl methacrylate (EMA) and styrene (St). Well-defined polymers with predetermined molecular weight and relatively narrow molecular weight distribution were synthesized. After polymerization, the supported cobalt (II) catalyst was easily and effectively removed from the polymerization system by simple centrifugation and very pure polymer products were obtained (Co residue <0.1 ppm). Using the obtained polymers as macroinitiators, polymerization of methyl methacrylate (MMA) and fluorinated methacrylate ether 2-[(perfluorononenyl)oxyl] ethyl methacrylate (FNEMA) were performed, respectively. Well-defined and pure diblock copolymers PBA-b-PMMA, PS-b-PMMA and PS-b-PFNEMA were synthesized.     

Kinetics of atom transfer radical polymerization of crosslinkable terpolymer P(MMA‐BA‐HEMA)

A crosslinkable terpolymer P(MMA‐BA‐HEMA) was prepared by atom transfer radical copolymerization of 2‐hydroxyethyl methacrylate, methyl methacrylate and butyl acrylate. The structure of the terpolymer was characterized by ¹H NMR and gel permeation chromatography. The effects on the polymerization of ligand, initiator, solvent, CuCl₂ added in the initial stage and reaction temperature were investigated. The optimal reaction conditions were ethyl 2‐bromopropionate as initiator, CuCl/PMDETA as catalyst, cyclohexanone as solvent, catalyst/ligand = 1:1.5, [M]₀:[I]₀ = 200:1 and temperature 70 °C. The reaction followed first‐order kinetics with respect to monomer concentration, indicating the best control over the polymerization process, a constant concentration of the propagating radical during the polymerization, efficient control over M_n of the polymer and low polydispersity (M_w/M_n < 1.3). © 2013 Society of Chemical Industry     

Viscoelastic properties of branched polyacrylate melts

The viscoelastic properties of poly(n‐butyl acrylate), poly(ethyl acrylate) and poly(methyl acrylate) melts have been studied using samples that varied in both molar mass and the mol% branched repeat units, these properties having been previously determined by gel permeation chromatography and ¹³C NMR spectroscopy, respectively. Poly(n‐butyl acrylate) was studied most extensively using seven samples; one sample of poly(n‐butyl acrylate), two samples of poly(ethyl acrylate) and one sample of poly(methyl acrylate) were used to study the effect of side‐group size. Storage and loss moduli were measured over a range of frequency (1 × 10^?3 to 1 × 10² rad s^?1) at temperatures from T_g + 20 °C to T_g + 155 °C and then shifted to form master curves at T_g + 74 °C through use of standard superposition procedures. The plateau regions were not distinct due to the broad molar mass distributions of the polyacrylates. Hence, the upper and lower limits of shear storage modulus from the nominal ‘plateau’ region of the curves for the seven poly(n‐butyl acrylate) samples were used to calculate the chain molar mass between entanglements, M_e, which gave the range 13.0 kg mol^?1 < M_e < 65.0 kg mol^?1. The Graessley–Edwards dimensionless interaction density and dimensionless contour length concentration were calculated for poly(n‐butyl acrylate) using the mean value of plateau modulus (1.2 × 10⁵ Pa) and three different methods for estimation of the Kuhn length; the data fitted closely to the Graessley–Edwards universal plot. The Williams–Landel–Ferry C₁ and C₂ parameters were determined for each of the polyacrylates; the data for the poly(n‐butyl acrylate) samples indicate an overall reduction in C₁ and C₂ as the degree of branching increases. Although the values of C₁ and C₂ were different for poly(n‐butyl acrylate), poly(ethyl acrylate) and poly(methyl acrylate), there is no trend for variation with structure. Thus the viscoelastic properties of the polyacrylate melts are similar to those for other polymer melts and, for the samples investigated, the effect of molar mass appears to dominate the effect of branching. © 2001 Society of Chemical Industry     

Mechanism of the polymerization of n-butyl acrylate initiated by N,N-diethyldithiocarbamate derivatives. Part 2. Investigation of the reaction mechanism

The polymerization of n-butyl acrylate (BuAc) initiated with a model compound (butyl-2-(N,N-diethyldithiocarbamyl)propionate, RTC) has been investigated. The living character of this polymerization has been assessed and compared with those of styrene and methyl methacrylate. The small variation of M_n with yield is explained by the faster propagation than for styrene and methyl methacrylate, which leads to slow initiation and extensive transfer to the initiator. Predominant reversible termination (or deactivation) of the growing chains by the dithiocarbamyl radicals gives, however, polymers of functionality near to unity, which are photoinitiated at the same rate as RTC and reinitiate the polymerization of BuAc with a linear growth of the M_n up to 40% yield. This is better than was obtained with methyl methacrylate. Side reactions also take place leading to a decrease of functionality, to the formation of tetraethylthiuram disulphide and of carbon disulphide. Possible mechanisms are proposed for the secondary reactions. © 1998 SCI.     

Synthesis and thermal properties of poly(methyl methacrylate)‐poly(L‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer

Poly(methyl methacrylate)‐poly(L ‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer was prepared using atom transfer radical polymerization (ATRP). The structure and properties of the copolymer were analyzed using infrared spectroscopy, gel permeation chromatography, nuclear magnetic resonance (¹H‐NMR, ¹³C‐NMR), thermogravimetry, and differential scanning calorimetry. The kinetic plot for the ATRP of methyl methacrylate using poly(L ‐lactic acid) (PLLA) as the initiator shows that the reaction time increases linearly with ln[M]₀/[M]. The results indicate that it is possible to achieve grafted chains with well‐defined molecular weights, and block copolymers with narrowed molecular weight distributions. The thermal stability of PLLA is improved by copolymerization. A new wash‐extraction method for removing copper from the ATRP has also exhibits satisfactory results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Solubility in the binary and ternary system for poly(alkyl acrylate)-supercritical solvent mixtures

Experimental cloud-point data to 210 ‡C and 2,200 bar are presented for binary and ternary mixtures of poly(methyl acrylate)-CO₂-methy acrylate and poly(ethyl acrylate)-CO₂, propylene, and 1-butene-ethyl aerylate systems. The accuracy of the experimental apparatus was tested by comparing the measured pressure-temperature phase behavior data of the poly(ethyl acrylate)-CO₂ system obtained in this study with those of Rindfleisch et al. [1995]. The phase behaviors for the system poly(methyl acrylate)-CO₂-methyl acrylate were measured in changes of pressure-temperature slope, and with cosolvent concentrations of 0, 5.0, 13.7, 25.3, and 43.3 wt%, respectively. With 48.3 wt% methyl acrylate to the poly(methyl acrylate)-CO₂ solution significantly changes, the phase behavior curve takes on the appearance of a typical lower critical solution temperature (LCST) boundary. The impact of ethyl acrylate on the cloud-point for the poly(ethyl acrylate)-CO₂ system shows the change of slope of the phase behavior curves from negative to positive with ethyl acrylate concentration of 0, 8.2, and 25.0 wt%. The cloud-point behavior for the poly(ethyl acrylate)-CO₂-39.5 wt% ethyl acrylate system shows an LCST curve. The solubility curve to ∼150 ‡C and 1,650 bar for poly(ethyl acrylate)-propylene-ethyl acrylate system shows the change of pressure-temperature diagram and with ethyl acrylate concentration of 0, 7.2 and 21.0 wt%. Also, when 41.1 wt% ethyl acrylate was added to the poly(ethyl acrylate)-propylene solution, the phase behavior curve showed the LCST region. The high pressure phase behavior of poly(ethyl acrylate)-1-butene-0, 3.1, 8.1, 18.5 and 30.7 wt% ethyl acrylate system presented the change of pressure-temperature curve from the UCST region to U-LCST region as the ethyl acrylate concentration increased.     

Effects of the cosurfactant 1‐butanol and feed composition on nanoparticle properties produced by microemulsion copolymerization of styrene and methyl methacrylate

The concentration of the cosurfactant 1‐butanol (BuOH) determined the polymer weight and size for a series of poly(styrene‐co‐methyl methacrylate)s (P(St‐co‐MMA)) synthesized by the free‐radical (o/w) microemulsion technique. A factorial design established the levels of the experimental conditions for the polymerization i.e., concentration of the surfactant, sodium dodecyl sulfate (SDS); concentration of the cosurfactant, BuOH; temperature and ratio of the styrene (St) to methyl methacrylate (MMA). An increase in the weight‐average molecular weight (M_w) and number‐average molecular weight (M_n) was observed in the P(St‐co‐MMA) series with an increase in BuOH concentration from 1 to 5 wt %. These effects could arise from the micellar aggregation induced by interfacial BuOH. The unique micellar conditions could be exploited to synthesize copolymers of varying molecular weight and size. Additionally, the composition of the copolymers was virtually templates of the feed composition. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

The homo and copolymerisation of 2-(dimethylamino)ethyl methacrylate in supercritical carbon dioxide

This paper describes the free radical dispersion homopolymerisation of 2-(dimethylamino) ethyl methacrylate (DMA) and copolymerisation of DMA with methyl methacrylate (MMA) in supercritical carbon dioxide (scCO₂). The polymerisations are performed in the presence of two commercially available stabilisers, poly(dimethylsiloxane) monomethacrylate macromonomer (PDMS-mma) and the carboxylic acid terminated perfluoropolyether (Krytox 157FSL). Dry, fine powdered polymer product was produced for the copolymer under optimised conditions, but only aggregated solid is formed for homo poly(DMA). The effect of reaction time, stabiliser, copolymer composition and reaction pressure on the yield, molecular weight and morphology of the copolymers has been investigated.