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     

Photocatalyzed Hydrogen Atom Transfer Degradation of Vinyl Polymers: Cleavage of a Backbone C−C Bond Triggered by Radical Activation of a C−H Bond in a Pendant

In this work, we achieved a triggering degradation of polymers composed of carbon-carbon (C−C) bonded backbone without relying on introduction of labile heteroatom-based bond. The crucial point for the achievement is using vinyl ether (VE) as a comonomer in radical copolymerization of (meth)acrylate for introduction of the carbon-hydrogen (C−H) bonds active for photocatalyzed hydrogen atom transfer (HAT) as triggers in the pendant. Interestingly, methyl methacrylate (MMA)-n-butyl vinyl ether (NBVE) copolymer underwent degradation in acetonitrile in the presence of benzophenone (Ph₂CO) under UV irradiation at 80 °C. The degradation did not take place, when any one of UV, Ph₂CO, heat, and NBVE unit was removed or HAT-active solvent such as toluene and 1,4-dioxane was used. These control experiments strongly supported the HAT-triggering degradation. Furthermore, the degradation behaviors of the copolymers with other vinyl ethers such as tert-butyl vinyl ether and methyl isopropenyl ether indicated that the C−H bond neighboring to oxygen on the pendant is mainly responsible for the trigger leading to degradation. The HAT-triggering degradation was also demonstrated even with the acrylate-based copolymer.     

Copolymerization of the cyclic monomer, 5,5-dichloro-4-hydroxy-2,4-pentadienoic acid lactone

The copolymerization of 5,5-dichloro-4-hydroxy-2,4-pentadienoic acid lactone with methyl methacrylate, methyl acrylate, vinyl acetate, and vinylidene chloride to give yellow to red copolymers is described. Infrared, nuclear magnetic resonance, and ultraviolet spectroscopy indicate that the polymerization of the lactone proceeds by a 1,4-addition mechanism, followed by hydrogen chloride elimination, to give a highly conjugated structural unit closely related to the structure of the original monomer. The intense colors of the copolymers may arise from conjugated sequences of lactone units or through further eliminations along comonomer sequences.     

Photothermal degradation of copolymers of methyl methacrylate and n-butyl acrylate

The photothermal degradation of copolymers of methyl methacrylate (MMA) and n-butyl acrylate (n-BuA) covering the whole composition range has been studied at 165°.The gaseous products, which are relatively minor, are hydrogen, carbon monoxide and methane. The liquid products are predominantly MMA, with n-BuA, n-butanol and n-butyraldehyde as minor products. Infra-red spectral changes in the residue were attributed to lactone formation and associated with butanol formation as in the purely thermal reaction The “cold ring” or chain fragment fraction becomes increasingly more abundant as the n-BuA content of the copolymer is increased.All the products and principal features of the reaction are explained in terms of a radical process which is initiated by scission of pendant acrylate units and is propagated by a combination of depropagation and intra- and intermolecular transfer processes, the relative importance of which depends upon copolymer composition. Differences from the thermal reaction and the corresponding reaction in copolymers of methyl methacrylate and methyl acrylate are discussed.     

Fluorinated and ring‐substituted bisbenzimidazole copper complexes for ethylene/acrylate copolymerization

Bisbenzimidazole copper dichloride complexes (CuBBIMs), when activated with methylaluminoxane, catalyze the random copolymerization of ethylene with acrylates to produce highly linear functional copolymers. To probe the sensitivity of the copolymerization to the catalyst structure, a series of CuBBIM catalysts with various steric, electronic, and geometric ligand characteristics was prepared, including CuBBIMs having benzimidazole ring substituents and ligand backbones of various lengths. Four different acrylates were also evaluated as comonomers (t‐butyl acrylate, methyl acrylate, t‐butyl methacrylate, and methyl methacrylate). Although no obvious ligand‐based influences on copolymerization were identified, the structure of the acrylate comonomer was found to exert significant effects. Copolymers prepared with t‐butyl methacrylate comonomer exhibited the highest ethylene contents (31–63%), whereas those prepared with methyl acrylate contained only minor amounts of ethylene (<15%). Copolymerizations carried out at lowered acrylate feed levels generally had increased ethylene contents but showed smaller yields, lowered molecular weights, and increased branching. Unusual ketoester structures were also observed in the methyl acrylate and methyl methacrylate containing copolymers, suggesting that the acrylate ester group size may be an important controlling factor for copolymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1817–1840, 2006     

Efficient synthesis of branched poly(acrylic acid) derivatives via postpolymerization modification

The utility of pentafluorophenyl esters for the selective introduction of functional units and branch points in well-defined poly(acrylic acid) (PAA) derivatives is demonstrated using a combination of controlled radical polymerization and postpolymerization modification. Reversible addition-fragmentation chain transfer enables the synthesis of well-defined copolymers—poly(pentafluorophenyl acrylate-co-tert-butyl acrylate)—with the active ester repeat units serving as attachment points for reaction with primary amines, specifically tris(2-(t-butoxycarbonyl)ethyl)methyl amine (Behera's amine). Deprotection using trifluoroacetic acid removes both the backbone and side chain t-butyl esters to give a series of branched PAA derivatives containing novel tricarboxylic acid side chains that are well suited to complexation and multidentate interactions. Surprisingly, the active ester homopolymer is shown to have the highest reactivity with Behera's amine when compared to copolymers with lower incorporation of pentafluorophenyl esters, suggesting an intriguing interplay of neighboring group effects and steric interactions. The ability to tune the efficiency of postpolymerization modification gives a library of PAA derivatives.     

Synthesis and utility of ethylene (meth)acrylate copolymers prepared by a tandem ring-opening polymerization hydrogenation strategy

One new and one established functional cyclooctene were prepared and (co)polymerized using ring-opening metathesis polymerization. The resulting polymers were hydrogenated to yield the corresponding functional polyolefins that were structurally equivalent to copolymers of ethylene and either methyl methacrylate, t-butyl acrylate, or acrylic acid after deprotection. The copolymers that incorporate methyl methacrylate into the backbone were used as compatibilizers for poly(methyl methacrylate)/polyethylene blends. The copolymers that incorporate t-butyl acrylate into the backbone yielded elastomers that could be thermally crosslinked. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3117–3126     

Synthesis and enzymatic degradation of 2‐methylene‐1,3‐dioxepane and methyl acrylate copolymers

Copolymers of 2‐methylene‐1,3‐dioxepane (MDO) and methyl acrylate (MA) containing ester units both in the backbone and as pendant groups were synthesized by free‐radical copolymerization. The influence of reaction conditions such as the polymerization time, temperature, initiator concentration, and comonomer feed ratio on the yield, molecular weight, and copolymer composition was investigated. The structure of the copolymers was confirmed by ¹H NMR, ¹³C NMR, and IR spectroscopy. Differential scanning calorimetry indicated that the copolymers had a random structure. An NMR study showed that hydrogen transfer occurred during the copolymerization. The reactivity ratios of the comonomers were r_MDO = 0.0235 and r_MA = 26.535. The enzymatic degradation of the copolymers obtained was carried out in the presence of proteinase K or a crude enzyme extracted from earthworms. The experimental results showed that the higher ester molar percentage in the backbone caused a faster degradation rate. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2898–2904, 2003     

Binary and ternary copolymers of norbornene and its derivatives with acrylates as novel materials for optoelectronics

The free-radical copolymerization of norbornene with methacrylate, tert-butyl acrylate, acrylic acid, and decyl acrylate and the benzoyl peroxide-initiated copolymerization of tert-butyl norbornenecar-boxylate and tert-butyl acrylate are studied for the first time. Novel binary and ternary copolymers are obtained, and experimental conditions (the temperature and time of reaction, initiator concentration, and comonomer ratio) affecting the compositions, molecular masses, glass-transition temperatures, and yields of the copolymers are determined. It is ascertained that the copolymers of norbornene with methyl acrylate and tert-butyl acrylate have high transparency (93?C94%) in the range 300?C800 nm. Because of this fact, the copolymers show promise as matrices for creation of nanocomposite materials suitable for optoelectronic applications.     

Investigation of viscoelastic and thermal properties of cyclic carbonate bearing copolymers

In this paper, one-pot reaction of radical copolymerization of glycidyl methacrylate with methyl methacrylate, n-butyl acrylate and styrene under carbon dioxide atmosphere (1 atm) was employed to synthesize cyclic carbonate bearing copolymers. Obtained copolymers were characterized using ¹H NMR and FTIR spectroscopy. The viscoelastic and thermal properties of the resulted copolymers were investigated using dynamic mechanical thermal analysis and thermogravimetric analysis. Copolymer composition and monomer type had a significant effect on the properties of the copolymers. An increase in cyclic carbonate (2-oxo-1,3-dioxolane-4-yl-methyl methacrylate) content in the copolymer composition led to an increase in glass transition temperature, storage modulus and loss tangent as well as the thermal stability of the copolymers.     

Radical alternating copolymerization of vinyl ethers

New alternating equimolar copolymers of electrophilic trisubstituted ethylenes, methyl 3-phenyl-2-cyanopropenoate and 2-phenyl-1,1-dicyanoethene, with ethyl, n-butyl, i-butyl, t-butyl, 2-chloroethyl, and phenyl vinyl ethers were prepared by free radical initiation. Chemical compositions of the copolymers are 1 : 1 in broad ranges of monomer ratios. The copolymerization rate of both electrophilic monomers with the vinyl ethers increase in the series 2-chloroethyl > ethyl > phenyl > n-butyl > i-butyl > t-butyl. These variations in the reactivity of the vinyl ethers are discussed in terms of their preferred conformations in donor-acceptor complexes with electrophilic trisubstituted ethylenes. © 1993 John Wiley & Sons, Inc.     

Alternating copolymerization of methyl acrylate with donor monomers having a protected amine group

Attempts were made to copolymerize p-aminostyrene, p-acetamidostyrene, N-methyl-p-aceta-midostyrene, N-(4-vinylphenyl) phthalimide, N-vinyl succinimide, and N-vinyl phthalimide with methyl acrylate complexed with ethyl aluminum sesquichloride. Only reactions involving N-(4-vinylphenyl)phthalimide and N-vinyl phthalimide yielded alternating copolymers. N-vinyl succinimide gave nonalternating copolymers insoluble in common solvents and the other monomers did not copolymerize. In some cases, the conventional radical copolymers were prepared for comparison purposes. The reactivity ratios of the free-radical initiated copolymerization of methyl acrylate (I) with N-(4-vinylphenyl)phthalimide (II) were r₁ = 0.14 and r₂ 1.56. The alternating copolymers were studied by ¹H-NMR and ¹³C-NMR spectroscopy. The alternating copolymer of N-(4-vinylphenyl)phthalimide with methyl acrylate was hydrazinolyzed to form the alternating copolymer of methyl acrylate with p-aminostyrene. Hydrazinolysis of the alternating copolymer of methyl acrylate with N-vinyl phthalimide removed the phthalimide moiety and generated vinyl amine units which readily cyclized with neighboring methyl acrylate units to form copolymers that contained five-membered lactam rings. The infrared (IR) spectra of the hydrazinolyzed products contain bands due to amine or amide groups and are devoid of the characteristic bands of the phthalimide ring.     

Functional polymethacrylates as bacteriostatic polymers

Two copolymers, P(PCEMA-co-MMA) and P(t-BMA-block-PCEMA), were prepared via ATRP using 2-(phenoxycarbonyloxy)ethyl methacrylate (PCEMA) as reactive monomer and methyl methacrylate (MMA) or tert-butyl methacrylate (t-BMA) as co-monomers. Alternatively phenoxycarbonyloxy decorated polymethacrylates were obtained via polymer analogous reaction: P(HEMA) was reacted with phenyl chloroformate to yield P(PCEMA). The highly reactive phenoxycarbonyloxy groups were used for polymer analogous reactions with nucleophiles to obtain polymers with ionic/hydrophilic and hydrophobic side groups. Different amines with long alkyl chains or tertiary amine groups were reacted with phenoxycarbonyloxy decorated polymers and subsequently reacted with methyl iodide to obtain amphipathic polymers with bacteriostatic properties.     

Synthesis of photochromic liquid-crystalline triblock copolymers by pseudoliving reversible addition-fragmentation chain-transfer polymerization

Symmetric photosensitive fully liquid-crystalline triblock copolymers are synthesized by pseudo-living reversible addition-fragmentation chain-transfer radical polymerization for the first time. The polymerization of 3-[methyl(phenyl)amino]propyl acrylate mediated by three different symmetric trithiocarbonates with various leaving groups is studied. It is shown that reversible addition-fragmentation chain-transfer agents make it possible to synthesize narrowly dispersed homopolymers with controlled molecular masses. Poly[(3-[methyl(phenyl)amino]propyl acrylate) trithiocarbonates] are used as polymeric reversible addition-fragmentation chain-transfer agents in the block copolymerization of the phenyl benzoate acrylic monomer. The chemical modification of block copolymers yields desirable photosensitive triblock copolymers containing azobenzene groups. The effect of the molecular structure of triblock copolymers on their phase behavior and thermal properties is examined.     

Photo-switchable azobenzene-functionalized block copolymers from atom transfer radical polymerizations

Diblock copolymers composed of monomers of tert-butyl acrylate and a side-chain azobenzenecontaining monomer, 4-[(E)-(4-nitrophenyl)diazenyl]phenyl prop-2-enoate were synthesized using atom transfer radical polymerization technique. Experimental strategy involved synthesis of block of tert-butyl acrylate macroinitiator followed by addition of second block of azobenzene-containing monomer to prepare desired block-copolymer. GPC analysis indicated narrow molecular weight distributions with degree of polymerization found in good agreement with targeted value. Prepared block copolymers of varying chain lengths can potentially be used to obtain morphologies that can find useful applications for biomedical applications including intriguing photo-switchable drug delivery systems.     

Degradation of vinylidene chloride/methyl acrylate/phenylacetylene (VDC/MA/PA) terpolymers. Effect of internal unsaturation on the stability of Saran copolymers

The thermal degradation of vinylidene chloride/methyl acrylate/phenylacetylene (VDC/MA/PA) terpolymers containing a constant 9 wt % methyl acrylate and small but varying amounts of phenylacetylene has been examined in the solid phase and in bibenzyl solution. Thermally promoted degradative dehydrochlorination, largely uncomplicated by methyl chloride formation, readily occurs at temperatures approaching 200°C. Incorporation of phenylacetylene into the polymer structure greatly facilitates degradative dehydrochlorination. Indeed, the presence of phenylacetylene induces the formation of polyene segments during the polymerization so that all the terpolymers, even at very low phenylacetylene loading, are tan in color. The decreased stability of polymers containing internal unsaturation arises from an increased rate of initiation for the degradation reaction. The propagation rate is largely unaffected by the level of unsaturation initially present in the polymer. Thus random double bonds have been identified as the principal defect sites responsible for the facile degradation of Saran copolymers. Species which promote the degradation of Saran polymers probably do so by facilitating the introduction of double bonds into the structure. The ratio of hydrogen chloride to stilbene formed for degradation of the terpolymers in bibenzyl solution is ca. 35:1. This is strongly reminiscent of PVDC degradation and suggests that for degradation of either the homopolymer or Saran copolymers the chain-carrying allylic radical pair does not dissociate to any appreciable extent as dehydrochlorination occurs.     

Grafting copolymerization of vinyl monomers on polyimide macroinitiators by the method of atom transfer radical polymerization

Graft copolymers with the main polyimide chain and side chains of poly(n-butyl acrylate), poly(tert-butyl acrylate), poly(methyl methacrylate), poly(tert-butyl methacrylate), polystyrene, and polystyrene-block-poly(methyl methacrylate) were synthesized by atom transfer radical polymerization on the multicenter polyimide macroinitiators in the presence of the halide complexes of univalent copper with nitrogen-containing ligands. Polymerization of metha-crylates is most efficiently developed on the polyimide macroinitiators. The obtained graft copolymers initiate the secondary polymerization (“post-polymerization”) of methyl methacrylate. The conditions of detachment of side chains of graft polymethacrylates that do not involve the ester groups of their monomeric units were found. The molecular mass characteristics of the graft copolymers and isolated polymers, being the detached side chains of the copolymers, were determined. The detached side chains of different chemical structures have low values of the polydispersity index. The procedure developed was used for the preparation of new graft polyimides with side chains of poly-4-nitro-4′-[N-methylacryloyloxyethyl-N′-ethyl]amino-azobenzene that cause the nonlinear optical properties and with the side chains of poly(N,N-dimethylaminoethyl methacrylate) that cause the thermosensitive properties of the copolymers.     

Stability of vinylidene chloride copolymers containing 4-vinylpyridine units

Vinylidene chloride copolymers are prominent in the barrier plastic packaging industry. These materials display excellent barrier to the transport of oxygen (and other small molecules) as well as flavor and aroma molecules. However, they suffer from a propensity to undergo degradative dehydrochlorination at process temperatures. To scavenge hydrogen chloride formed and prevent its interaction with the metallic components of process equipment, a passive base is usually included as an additive prior to processing. The base is most often an inorganic oxide or salt. These may negatively impact the properties of the polymer, particularly as a film. An organic base that could be covalently incorporated into the copolymer might display better behavior. Accordingly, a series of copolymers containing low levels of 4-vinylpyridine (0.05–3 mole%) have been prepared, characterized, and examined by thermogravimetry to assess thermal stability. In all cases, polymers containing 4-vinylpyridine units are less stable than the polymer containing none of this comonomer. Clearly, the pyridine moiety is a sufficiently strong base to promote E2 elimination of hydrogen chloride to generate dichlormethylene units in the mainchain from which thermal degradation may be initiated.     

BARRIER PROPERTIES OF VINYLIDENE CHLORIDE COPOLYMERS

The permeability coefficients of a series of copolymers of vinylidene chloride (VDC)with methyl acrylate (MA), butyl acrylate (BA) or vinyl chloride (VC) (as comonomer)to oxygen and carbon dioxide have been measured at 1.0 MPa and 30℃, while those towater vapor have been measured at 30℃ and 100% relative humidity All the copolymersare semicrystalline. VDC/MA copolymers have lower melting temperature compared withVDC/BA copolymers, while that melting temperature of VDC/VC copolymer is higherthan that of VDC/acrylate copolymers with the same VDC content. The barrier propertyof the copolymers is predominantly controlled by crystallite, free volume fraction, andcohesive energy The permeability coefficients of VDC/MA copolymers to oxygen, carbondioxide, and water vapor were successfully correlated with the ratio of free volume tocohesive energy.     

Structural defects in polyvinylchloride—II Structure and properties of polyvinylchloride prepared in presence of oxygen and carbon monoxide

To investigate oxygen-containing structures in PVC, arising for example from the presence of air in technical polymerization vessels, vinyl chloride (VC) suspension polymerizations were performed with various amounts of added oxygen. Quantitative investigations demonstrated that the low molecular peroxides formed in the induction period decompose, resulting in hydrogen chloride, formaldehyde and carbon monoxide. Residual peroxides have been determined in the final copolymers and found to be mainly responsible for the considerable reduction in the thermal stability. Considerable evidence is provided that carbon monoxide, copolymerized with VC, is incorporated as a carboxylic acid sidegroup. It is considered to arise from a 1,2 chlorine shift to the carbonyl radical chain-end. The resulting acryloyl chlorides are capable of reacting with water, alcohols or amines to yield the corresponding acids, esters or amides. A new i.r. band at 1770 cm^?1 after alkali treatment of VC-CO copolymers containing acrylic acid groups is suggested as caused by the formation of butyrolactone structures. Butyrolactone formation by methyl chloride evolution was also observed in thermal degradation of VC-CO copolymers containing methyl acrylate units. The rates of dehydrochlorination of the copolymers are not very different from those of pure suspension PVC.