Surface grafting of polyethylene by mutual irradiation in methyl acrylate vapor. I. γ irradiation

Mutual irradiation of polyethylene (PE) in methyl acrylate vapor easily forms a poly(methyl acrylate) (PMA) homopolymer layer on the inner graft copolymer layer consisting of both PE and PMA components as a result of the rapidly increasing surface-graft composition. This growth process of surface grafting has been found to provide some specific kinetic features different from those in other surface-grafting systems. With formation of the surface homopolymer layer, low- and highdensity PE sheets give the same grafting rate, whereas both sheets give different rates in grafting stages or conditions in which the homopolymer layer is not formed. This result indicates that most monomers, penetrating across the surface, are entrapped or consumed in the surface homopolymer layer; accordingly the rate becomes independent of the type of PE sheets that have significantly different diffusion coefficients. The thickness of the inner graft copolymer layer, which is kept constant after homopolymer-layer formation, increases with decreasing dose rate and with increasing monomer vapor pressure and temperature. This behavior can be qualitatively explained according to an equation for the initial steady-state grafting depth.     

Surface grafting of polyethylene by mutual irradiation in methyl acrylate vapor. II. High-energy electrons irradiation

Vapor-phase mutual grafting of methyl acrylate (MA) onto polyethylene (PE) at high dose rates from an electron accelerator yields the same surface graft structure as does the grafting at low dose rates from ⁶⁰Co sources; i.e., a homopolymer layer (consisting of only MA component) is easily formed on the inner graft copolymer layer (consisting of both MA and PE components) as a result of the continuously increasing surface graft composition. To produce the surface layer, 4-MeV electron irradiation with a linear electron accelerator requires only less than 3 min of irradiation time at dose rates of more than 2 Mrad/min, whereas γ irradiation with a ⁶⁰Co source requires at least 1 hr at dose rates of less than 2 × 10³ rad/min. The rate of monomer consumption (or polymerization) in the surface homopolymer layer shows no dependence of irradiation time and a positive dependence of dose rate. It has been suggested that this kinetic feature at the high dose rates shows some contribution of vapor-phase homopolymerization and subsequent deposition (onto the grafting surface) followed by recombination with the grafted side chain radicals, although secondary graft copolymerization from the grafted chain radicals is still the principal process for the growth of the surface homopolymer layer.     

Surface grafting of polyethylene by mutual irradiation in methyl acrylate vapor. IV. Kinetic analysis by quartz helix microbalances

A detailed kinetic study of the γ-ray-induced surface grafting of methyl acrylate (MA) onto polyethylene (PE) has been investigated by using quartz helix microbalances. Under typical graft conditions, the grafting rate increases, levels off, and then accelerates with irradiation time; i.e., the typical growth process of the surface grafting consists of an initial stage having an increasing rate of grafting, an intermediate stage having a constant rate, and an advanced stage having an accelerated rate. A homopolymer layer (consisting only of an MA component) begins to be formed on the inner graft copolymer layer (consisting both of MA and PE components) at the transition zone in grafting rate after a duration of a constant rate of grafting. Therefore, the increasing rate in increasing rate in the intial stage of grafting reflects the graft copolymerization in the graft copolymer layer (inside the PE sheet), and the increasing rate in the advanced stage reflects the growth of the homopolymer layer. Under grafting reflects the graft tage reflects the growth of the homopolymer layer. Under grafting conditions by which the homolymer layer is not formed throughout the whole grafting process, the surface grafting remains remains in the initial stage. On the order hand, under grafting conditions by which the homopolymer layer begins to be formed from an early stage of grafting, the surface grafting proceeds rapidly from the initial stage to the advanced stage and thus skips the intermediate stage.     

淀粉与丙烯酸甲酯的接枝共聚物作为生物降解塑料的研究

如何解决废弃塑料制品的再资源化和使用无污染的降解塑料是当今人类急待解决的热点课题．淀粉与丙烯酸甲酯（MA）进行接技共聚以制备塑料发泡产品的研究已有报道［‘－‘1，一般认为塑料中淀粉含量在40％以上的产品，很容易在土壤中被微生物降解掉［‘］．这些研究都是在水溶液体系中进行的，本文的目的在于开发高淀粉含量的接校共聚物，为此对比了在3种不同体系（MA－CH3OHA12O三元均相溶液体系，水溶液体系和乳液体系）中得到的接校共聚物的力学性能、形态观察与组成情况，发现单纯追求高接技效率与接枝链MA的高分子量并不一定能得到…     

Controlled polymerization of methyl acrylate for high‐molecular‐weight polymers by pentafluorophenylbis(triflyl)methane‐promoted group transfer polymerization using triisopropylsilyl ketene acetal

The group transfer polymerization (GTP) of methyl acrylate (MA) was studied using pentafluorophenylbis(triflyl)methane (C₆F₅CHTf₂) as the organocatalyst and 1‐trimethylsiloxy‐, 1‐triethylsiloxy‐, and 1‐triisopropylsiloxy‐1‐methoxy‐2‐methyl‐1‐propene (MTS^Me, MTS^Et, and MTS^iPr, respectively) as the initiators. The C₆F₅CHTf₂‐promoted GTP of MA using MTS^iPr proceeded in a living nature to produce poly(methyl acrylate)s (PMAs) with controlled molecular weights and narrow molecular weight distributions, which allowed the synthesis of high‐molecular‐weight PMA with the number‐average molecular weight (M_n(SEC)) of up to 108,000 and the polydispersity (M_w/M_n) of 1.07. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry measurement revealed that the obtained PMA possessed the chain end structure that originated from MTS^iPr, showing that the C₆F₅CHTf₂‐promoted GTP of MA proceeded without any side reactions. In addition, the kinetic study and the postpolymerization experiment supported the living manner of the polymerization. Moreover, the block copolymerization of MA and n‐butyl acrylate (nBA) smoothly proceeded to afford the well‐defined PMA‐block‐poly(n‐butyl acrylate) (PnBA). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Aspects of Living Radical Polymerization Mediated by Cobalt Porphyrin Complexes

Living radical polymerization (LRP) of methyl acrylate (MA), acrylic acid (AA), and vinyl acetate (VAc) mediated by cobalt(II) porphyrin complexes ((TMP)Co^II·, (TMPS)Co^II·) are reported. The polymeric products with relatively low polydispersity and controlled number average molecular weight (M_n) based on one polymer chain per cobalt complex demonstrate the living characters of the polymerization process. The formation of block copolymers of poly(methyl acrylate)‐b‐poly(vinyl acetate) (PMA‐b‐PVAc) and poly(methyl acrylate)‐b‐poly(vinyl pyrrolidone) (PMA‐b‐PVP) demonstrate another important feature of LRP and extend the application of cobalt porphyrin mediated radical polymerization to a wider array of functionalized monomers. Kinetic studies using ¹H NMR to follow the formation of orGano‐cobalt complexes reveal that two mechanisms, reversible termination (RT) and degenerative transfer (DT), occur during the polymerization process. MA and VAc polymerization mediated by cobalt porphyrin complexes are used to illustrate the properties of these two LRP pathways and evaluate the kinetic and thermodynamic properties for several of the central reactions.     

Solution properties of poly(methyl acrylate) and (1:1) poly(styrene-co-methyl acrylate)

Poly(methyl acrylate) (PMA) and 1:1 poly(styrene-co-methyl acrylate) (PSMA) were prepared by solution and bulk polymerization, respectively. The copolymer was analyzed with NMR to ascertain its composition and microstructure. The solution properties of unfractionated PMA and fractionated PSMA in ethyl acetate were investigated by light-scattering and viscosity techniques at 35°C. Narrow composition heterogeneity as revealed from the light-scattering measurements in different solvents justified the use of a single solvent for the copolymer characterization. The equations relating the limiting viscosity number to molecular weight, the molecular dimension to molecular weight, etc., were found for homopolymer and copolymers in ethyl acetate at 35°C. In the evaluation of the Flory constant K for the unperturbed state by methods based on Flory-Fox-Schaefgen, Kurata-Stockmayer, and Stockmayer-Fixman expressions, only the first method gave a value for PMA in ethyl acetate, consistent with that obtained in other solvents, whereas similar values of K were obtained by the three methods for PSMA in ethyl acetate. The studies indicate reduced thermodynamic interaction for PSMA–ethyl acetate compared to PMA–ethyl acetate, but increased steric effect in the copolymer compared with the homopolymer.     

New initiator system for the anionic polymerization of (meth)acrylates in toluene. IV. Random copolymerization of (meth)acrylates in toluene initiated by s-BuLi ligated by lithium silanolates

Copolymerization of binary mixtures of alkyl (meth)acrylates has been initiated in toluene by a mixed complex of lithium silanolate  (s-BuMe₂SiOLi) and s-BuLi (molar ratio > 21) formed in situ by reaction of s-BuLi with hexamethylcyclotrisiloxane (D₃). Fully acrylate and methacrylate copolymers, i.e., poly(methyl acrylate-co-n-butyl acrylate), poly(methyl methacrylate-co-ethyl methacrylate), poly(methyl methacrylate-co-n-butyl methacrylate), poly(methyl methacrylate-co-n-butyl methacrylate), poly(isobornyl methacrylate-co-n-butyl methacrylate), poly(isobornyl methacrylate-co-n-butyl methacrylate) of a rather narrow molecular weight distribution have been synthesized. However, copolymerization of alkyl acrylate and methyl methacrylate pairs has completely failed, leading to the selective formation of homopoly(acrylate). As result of the isotactic stereoregulation of the alkyl methacrylate polymerization by the s-BuLi/s-BuMe₂SiOLi initiator, highly isotactic random and block copolymers of (alkyl) methacrylates have been prepared and their thermal behavior analyzed. The structure of isotactic poly(ethyl methacrylate-co-methyl methacrylate) copolymers has been analyzed in more detail by Nuclear Magnetic Resonance (NMR). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2525–2535, 1999     

Effect of Acetylene on the γ-Ray Crosslinking Polymerization of Various Kinds of Acrylic Monomers

The γ-radiation-induced crosslinking polymerization of methyl methacrylate (MMA), methacrylic acid (MAA), 2-hydroxyethyl methacrylate (HEMA), methyl acrylate (MA), and acrylic acid (AA) was carried out in bulk. The polymerization rates of AA and HEMA were much larger than those of other monomers. Acetylene had no influence on the polymerization rate in the initial stage, and the rate was dependent only on the kinds of monomers. In the absence of acetylene, gelation took place in PMA, PAA, and PHEMA obtained at complete conversion, but not in PMMA and PMAA. By the addition of acetylene, complete gelation of PMMA was observed, but no gel formation was observed for PMAA. Volume and weight swelling ratios were measured for PMA, PAA, PHEMA, and PMMA with complete gelation. It was found that by the addition of acetylene the molar concentration of crosslinks increased as much as about twice for PMA and PHEMA, and over about one hundred times for PMMA AND PAA. The relation between volume S_v and weight swelling ratio S_w was studied theoretically. S_v was expressed by the the equation, S_v = (p_p /p+)S_w+ (1 -p_p/p_s), as a function of S_w and the densities of pure polymer (p_p) and solvent (p_s) in swollen polymer.     

Substituted propenyl end groups as reactive intermediates in radical polymerization

The addition of propagating radicals of methyl acrylate (MA) and styrene (St) to CH₂?C(CO₂CH₃)CH₂? and CH₂?C(C₆H₅)CH₂? ω‐end groups of poly(methyl methacrylate) (PMMA) and polystyrene (PSt) was investigated. The end groups were as reactive as MA and St toward the poly(methyl acrylate) (PMA) and PSt radicals, respectively. The adduct radical derived from the two types of PMMA end groups and PMA radicals underwent β fragmentation exclusively to yield PMMA radicals and end groups bound to PMA chains. The addition of PSt radicals to PMMA with CH₂?C(CO₂Me)CH₂? end groups resulted in adduct radicals that underwent β fragmentation and addition to St or coupling with PSt radicals. Adduct radicals formed by the addition of PMA radicals to both types of end groups of PSt exclusively formed C? C bond by coupling with PMA radicals to form branched structures or by addition to MA monomer to give a copolymer. The fate of the adduct radicals was highly dependent on the type of polymer chain and the substituent bound to the end group. Steric congestion of the adduct radical arising from the α‐methyl group of the PMMA chain was considered to be crucial for fragmentation to expel the PMMA radical. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 645–654, 2003     

Melt spinning of propylene carbonate‐plasticized poly(acrylonitrile)‐co‐poly(methyl acrylate)

The primary use of poly(acrylonitrile) (PAN) fibers, commonly referred to as acrylic fibers, is in textile applications like clothing, furniture, carpets, and awnings. All commercially available PAN fibers are processed by solution spinning; however, alternative, more cost‐effective processes like melt spinning are still highly desired. Here, the melt spinning of PAN‐co‐poly(methyl acrylate) (PMA) plasticized with propylene carbonate (PC) at 175°C is reported. The use of methyl acrylate (MA) as comonomer and PC as an external plasticizer renders the approach a combination of internal and external plasticization. Various mixtures of PAN and PC used in this work were examined by rheology, subjected to melt spinning, followed by discontinuous and continuous washing, respectively. The best fibers were derived from a PAN‐co‐PMA copolymer containing 8.1 mol‐% of MA having a number‐average molecular weight M _n of 34 000 g/mol, spun in the presence of 22.5 wt.‐% of PC. The resulting fibers were analyzed by scanning electron microscopy and wide‐angle X‐ray scattering (WAXS), and were subjected to mechanical testing.     

Side-chain crystallinity. III. Influence of side-chain crystallinity on the glass transition temperatures of selected copolymers incorporating n-octadecyl acrylate or vinyl stearate

The influence of side-chain crystallinity on the glass transition temperatures of selected copolymers was investigated. The copolymers were selected, in part, from those whose crystallinity was treated in the preceding paper. These included the lower amorphous acrylate esters, such as methyl, ethyl, n-butyl, and 2-ethylhexyl acrylates, together with methyl methacrylate and acrylonitrile, each copolymerized with n-octadecyl acrylate over the range of composition. The decline in the glass transition temperature was linear with increasing weight fraction of n-octadecyl acrylate for all systems in the composition range where the copolymers were essentially amorphous. The extrapolated T_g for the amorphous state of poly(n-octadecyl acrylate), and for amorphous poly(oleyl acrylate), was close to ?111°C. This coincided with a value previously obtained by an extrapolation of data on homologs. Beyond a critical fraction of octadecyl acrylate (0.3 to 0.5), developing side-chain crystallinity in n-octadecyl acrylate raised the glass temperature steadily for all systems, up to a value of 17-C, obtained for the crystalline homopolymer. Crystallinity did not develop in stiff copolymers until T_g was about 30°C below the melting point of the most perfect crystals. In compositionally heterogeneous copolymers incorporating vinyl stearate, blocks of crystalline units appeared to be dispersed in a glassy matrix of amorphous co-units. An empirical equation was derived which fitted the experimental data for random copolymers, over all composition ranges, with fair accuracy.     

Thermal stability of copolymers of vinyl acetate and methyl acrylate

The thermal degradation of a series of copolymers of vinyl acetate and methyl acrylate and the two homopolymers poly(vinyl acetate) and poly(methyl acrylate) obtained using Ce(IV) as initiator has been investigated using differential thermal analysis (DTA) and thermogravimetry (TGA) in dynamic nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The stability increases as the methyl acrylate content in the copolymer composition increases. The incorporation of 5 mol % of vinyl acetate in the copolymer produces a marked decrease in stability compared to the homopolymer poly(methyl acrylate). There is evidence for an intramolecular lactonization process in vinyl acetate—methyl acrylate copolymers.     

Determination of the reactivity ratios of methyl acrylate with the vinyl acetate,vinyl 2,2-dimethyl-propanoate,and vinyl 2-ethylhexanoate

The course of composition drift in copolymerization reactions is determined by reactivity ratios of the contributing monomers. Since polymer properties are directly correlated with the resulting chemical composition distribution, reactivity ratios are of paramount importance. Furthermore, obtaining correct reactivity ratios is a prerequisite for good model predictions. For vinyl acetate (VAc), vinyl 2,2-dimethyl-propanoate also known as vinyl pivalate (VPV), and vinyl 2-ethylhexanoate (V2EH), the reactivity ratios with methyl acrylate (MA) have been determined by means of low conversion bulk polymerization. The mol fraction of MA in the resulting copolymer was determined by ¹H-NMR. Nonlinear optimization on the thus-obtained monomer feed–copolymer composition data resulted in the following sets of reactivity ratios: r_MA = 6.9 ± 1.4 and r_VAc = 0.013 ± 0.02; r_MA = 5.5 ± 1.2 and r_VPV = 0.017 ± 0.035; r_MA = 6.9 ± 2.7 and r_V2EH = 0.093 ± 0.23. As a result of the similar and overlapping reactivity data of the three methyl acrylate–vinyl ester monomer systems, for practical puposes these data can be described with one set of reactivity data. Nonlinear optimization of all monomer feed–copolymer composition data together resulted in r_MA = 6.1 ± 0.6 and r_VEst = 0.0087 ± 0.023. © 1994 John Wiley & Sons, Inc.     

Applications of ESCA to polymer chemistry. X. Core and valence energy levels of a series of polyacrylates

The core and valence levels of a series of poly(alkyl acrylates) have been studied by ESCA. From an analysis of the individual component peaks for the C_1s and O_1s core levels and from comparison of relative area ratios it is shown that ESCA may be applied to the study of surface compositions. The evidence presented strongly suggests that on the ESCA depth-profiling scale the technique statistically sample the repeat units with no evidence for preferential orientation of side chains at the surface. For some samples, ESCA provides evidence for a degree of surface oxidation and hydrocarbon contamination. The valence energy levels are shown to be characteristic of the polymer system. The measured absolute and relative binding energies of the core levels have been compared with model calculations using the charge-potential model in the CNDO/2 SCF MO formalism.     

Poly(acrylate‐b‐styrene‐b‐isobutylene‐b‐styrene‐b‐acrylate) Block Copolymers via Carbocationic and Atom Transfer Radical Polymerizations

A series of polyacrylate‐polystyrene‐polyisobutylene‐polystyrene‐polyacrylate (X‐PS‐PIB‐PS‐X) pentablock terpolymers (X=poly(methyl acrylate) (PMA), poly(butyl acrylate) (PBA), or poly(methyl methacrylate) (PMMA)) was prepared from poly (styrene‐b‐isobutylene‐b‐styrene) (PS‐PIB‐PS) block copolymers (BCPs) using either a Cu(I)Cl/1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) or Cu(I)Cl/tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) catalyst system. The PS‐PIB‐PS BCPs were prepared by quasiliving carbocationic polymerization of isobutylene using a difunctional initiator, followed by the sequential addition of styrene, and were used as macroinitiators for the atom transfer radical polymerization (ATRP) of methyl acrylate (MA), n‐butyl acrylate (BA), or methyl methacrylate (MMA). The ATRP of MA and BA proceeded in a controlled fashion using either a Cu(I)Cl/PMDETA or Cu(I)Cl/Me₆TREN catalyst system, as evidenced by a linear increase in molecular weight with conversion and low PDIs. The polymerization of MMA was less controlled. ¹H‐NMR spectroscopy was used to elucidate pentablock copolymer structure and composition. The thermal stabilities of the pentablock copolymers were slightly less than the PS‐PIB‐PS macroinitiators due to the presence of polyacrylate or polymethacrylate outer block segments. DSC analysis of the pentablock copolymers showed a plurality of glass transition temperatures, indicating a phase separated material.     

Synthesis of poly(glycerol)‐block‐poly(methyl acrylate) multi‐arm star polymers

Novel polyfunctional macroinitiators for atom transfer radical polymerization (ATRP) were obtained via esterification of hyperbranched polyglycerol (PG) (M_n = 4 770 g/mol, M_w/M_n = 1.5) with 2‐bromoisobutyryl bromide. Such macroinitiators were used in the presence of CuBr/pentamethyldiethylenetriamine (PMDETA) to initiate methyl acrylate (MA) polymerization, resulting in multi‐arm block copolymers with polyether core and 45–55 PMA arms. PMA arm length was controlled via monomer/initiator ratio and conversion (< 35%). Polymers were characterized by ¹H NMR, ¹³C NMR, SEC, membrane osmometry and DSC.     

o‐nitrobenzyl acrylate is polymerizable by single electron transfer‐living radical polymerization

Polymers containing o‐nitrobenzyl esters are promising for preparation of light sensitive materials. o‐Nitrobenzyl methacrylate has already been polymerized by controlled ATRP or RAFT. Unfortunately, the radical polymerization of o‐nitrobenzyl acrylate (NBA) was not controlled until now due to inhibition and retardation effects coming from the nitro‐aromatic groups. Recent developments in the Single Electron Transfer–Living Radical Polymerization (SET–LRP) provide us an access to control this NBA polymerization and living character of this NBA SET–LRP is demonstrated. Effects of CuBr₂ and ligand concentrations, as well as Cu(0) wire length on SET–LRP kinetics are shown presently. A first‐order kinetics with respect to the NBA concentration is observed after one induction period. SET–LRP proceeds with a linear evolution of molecular weight and a narrow distribution. High initiation efficiency close to 1 and high chain‐end functionality (～93%) are reached. Chain extension of poly(o‐nitrobenzyl acrylate) is realized with methyl acrylate (MA) to obtain well defined poly(o‐nitrobenzyl acrylate)‐b‐poly(methyl acrylate) (PNBA‐b‐PMA). Finally, light‐sensitive properties of PNBA are checked upon UV irradiation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2192–2201     

A novel azo‐containing dithiocarbamate used for living radical polymerization of methyl acrylate and styrene

A novel azo‐containing dithiocarbamate, 1‐phenylethyl N,N‐(4‐phenylazo) phenylphenyldithiocarbamate (PPADC), was successfully synthesized and used to mediate the polymerization of methyl acrylate (MA) and styrene (St). In the presence of PPADC, the reversible addition‐fragmentation chain transfer (RAFT) polymerization was well controlled in the case of MA, however, the slightly ill‐controlled in the case of St. Interestingly, the polymerization of St could be well‐controlled when using PPADC as the initiator in the presence of CuBr/PMDETA via atom transfer radical polymerization (ATRP) technique. In the cases of RAFT polymerization of MA and ATRP of St, the kinetic plots were both of first‐order, and the molecular weight of the polymer increased linearly with the monomer conversion while keeping the relatively narrow molecular weight distribution (M_w/M_n). The molecular weight of the polymer measured by gel permeation chromatographer (GPC) was also close to the theoretical value (M_n(th)). The obtained polymer was characterized by ¹H‐NMR analysis, ultraviolet absorption, FTIR spectra analysis and chain‐extension experiments. Furthermore, the photoresponsive behaviors of azobenzene‐terminated poly(methyl acrylate) (PMA) and polystyrene (PS) were similar to PPADC. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5626–5637, 2008     

Michael additions to acrylonitrile,methyl acrylate and methyl vinyl ketone to Nb-benzylidenetryptophan methyl ester

Michael addition to methyl acrylate and methyl vinyl ketone of N_b-benzylidene-L-tryptophan methyl ester 1 gave 2-(3-indolylmethyl)glutamic dimethyl ester 2a and α-(3-oxobutyl)tryptophan methyl ester 2b respectively. Addition to acrylonitrile of 1 yielded α,N_a-dicyanoethyltryptophan methyl ester 3 .