Poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)-g-poly(vinyl pyrrolidone): synthesis and characterization

Pluronic poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers are grafted with poly(vinyl pyrrolidone) by free radical polymerization of vinyl pyrrolidone with simultaneous chain transfer to the Pluronic in dioxane. This modified polymer has both thermal responsiveness and remarkable capacity to interact with a wide variety of hydrophilic and hydrophobic pharmaceutical agents which is very attractive for medical applications. The chemical structure of the graft copolymers was characterized by FTIR and 1H NMR spectroscopy. Polymerization conditions such as initiators, feed ratio, and reaction times are studied to obtain the ideal graft copolymer.     

Sequence distribution of partially hydrolyzed poly(vinyl acetate)

Copolymers of vinyl acetate and vinyl alcohol were studied by differential thermal analysis. The melting points of the copolymers are not a simple function of the composition, but depend on the method of preparation of the copolymers. Partial saponification of poly(vinyl acetate) with sodium hydroxide leads to high melting, ordered copolymers, while reacetylation of poly(vinyl alcohol) leads to low melting, random copolymers. Catalytic alcoholysis of PVAc yields copolymers intermediate in melting point and order. The results are treated by assuming that equal melting points indicate similar sequence length distributions of crystallizable units.     

Thermoxidative degradation of vinyl alcohol/vinyl acetate copolymers. IV. Statistical copolymers

The thermoxidative degradation of vinyl acetate/vinyl alcohol statistical copolymers was studied under dynamic thermal conditions and compared with that of block copolymers. The dependence of thermal characteristics or kinetic parameters on the content of ? OH groups of copolymers was established.     

Graft copolymerization. I. Grafting of hydroxyalkyl methacrylates on poly(vinyl alcohol)

New graft copolymers were synthesized by grafting hydroxyethyl methacrylate and hydroxpropyl methacrylate on poly(vinyl alcohol) in aqueous solution with Ce⁺⁴ions as initiator. The dependence of the percentage of grafting and monomer conversion on the concentration of the monomer, on the concentration of the initiator, on the total concentration of the reactants, and on temperature and duration of the reaction were investigated. Some basic properties of the graft copolymers and some preliminary permeation measurements of water vapors through films, made from these copolymers, are also reported.     

Multidimensional chromatographic techniques for hydrophilic copolymers II. Analysis of poly(ethylene glycol)-poly(vinyl acetate) graft copolymers

A large variety of hydrophilic copolymers is applied in different fields of chemical industry including bio, pharma and pharmaceutical applications. For example, poly(ethylene glycol)-poly(vinyl alcohol) graft copolymers that are used as tablet coatings are responsible for the controlled release of the active compounds. These copolymers are produced by grafting of vinyl acetate onto polyethylene glycol (PEG) and subsequent hydrolysis of the poly(ethylene glycol)-poly(vinyl acetate) graft copolymers. The poly(ethylene glycol)-poly(vinyl acetate) copolymers are distributed with regard to molar mass and chemical composition. In addition, they frequently contain the homopolymers polyethylene glycol and polyvinyl acetate. The comprehensive analysis of such complex systems requires hyphenated analytical techniques, including two-dimensional liquid chromatography and combined LC and nuclear magnetic resonance spectroscopy. The development and application of these techniques are discussed in the present paper.     

Thermal analysis and FT‐IR studies of adsorbed poly(ethylene‐stat‐vinyl acetate) on silica

Adsorbed poly(ethylene‐stat‐vinyl acetate) (PEVAc) on fumed silica was studied using temperature‐modulated differential scanning calorimetry (TMDSC) and FT‐IR spectroscopy. The properties of the copolymers were compared with poly(vinyl acetate) (PVAc) and low density polyethylene (LDPE) as references. TMDSC analysis of the copolymer‐silica samples in the glass transition region was complicated for the copolymers because of the ethylene crystallinity. Nevertheless, examination of the glass transition region for small adsorbed amounts of these copolymers indicated the presence of tightly‐ and loosely‐bound polymer segments, similar to other polymers which have an attraction to silica. Compared with bulk polymers with the same composition, the tightly‐bound polymers showed an increased glass transition temperature (T_g) and a loosely‐bound fraction with a lower T_g than bulk. FT‐IR spectra of the surface copolymers indicated that the fraction of bound carbonyls (p) increased as the fraction of vinyl acetate in the copolymers decreased, consistent with the notion that the carbonyls from vinyl acetate preferentially find their way to the silica surface. Spectra from samples with different adsorbed amounts of polymer were used to obtain the amount of bound polymer (M_b) and the ratio of molar absorption coefficients of bound carbonyls to free carbonyls (X). The copolymers had very large p values (up to 0.8) at small adsorbed amounts and dependent on the composition of the polymer. However, an analysis of the bound fractions, based on only the vinyl acetate groups, superimposed the data, suggesting that the ethylene units simply dilute the vinyl acetate groups in the surface polymer. The sample with the smallest fraction of vinyl acetate did not show this behavior and may be considered to be “carbonyl poor.” © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 727–736     

Solution behavior of [(ethylene-co-vinyl alcohol)-g-ethylene oxide] graft copolymers

The solution behavior of hydrophobic-hydrophilic water-soluble graft copolymers consisting of poly[(ethylene-co-vinyl alcohol)-g-ethylene oxide] was investigated by high-resolution NMR spectroscopy and measurements of solution viscosity in tetrahydrofuran, water, and mixtures thereof at various temperatures. A graft copolymer with a backbone containing 2.7 mole% vinyl alcohol exists in an intramolecular phase-separated conformation in aqueous solution, independent of the temperature. Graft copolymers with backbones containing 20.3 mol% vinyl alcohol exhibit an intramolecular mixed-phase conformation in which the mobility of chains in the hydrophobic region depends on temperature. The temperature dependence of the intrinsic viscosity in water shows a maximum near 50°C.     

Synthesis and polymerizations of methyl 3,3-difluorocyclobutene-1-carboxylate and methyl 3,3,4,4-tetrafluorocyclobutene-1-carboxylate

Two new monomers, methyl 3,3-difluorocyclobutene-1-carboxylate (MDFC) and methyl 3,3,4,4-tetrafluorocyclobutene-1-carboxylate (MTFC), were synthesized. Under free radical conditions, MDFC gave homopolymer; MTFC did not. Copolymerizations of these monomers showed them to behave as very electron-deficient monomers, MTFC more so than MDFC. MDFC copolymerized with various vinyl ethers and styrenes to give high yields of almost 1:1 copolymers. Acrylonitrile copolymerized in lower yield with less incorporation of MDFC; trimethylethylenetricarboxylate did not copolymerize. Bicyclobutane-1-carbonitrile copolymerized well. MTFC copolymerized with the very electron-rich monomers t-butyl vinyl ether and p-methoxystyrene, leading to alternating and nearly alternating copolymers, respectively, and even styrene tended to give almost 1:1 copolymers. Acrylonitrile gave only polyacrylonitrile, and trimethylethylenetricarboxylate did not react with MTFC under free radical conditions. The reaction of MTFC with the electron-rich monomers t-butyl vinyl ether and p-methoxystyrene occurred spontaneously via charge transfer complexes. Thermally, the copolymers were rather stable, those of MTFC more so than those of MDFC.     

Solution polymerization of vinyl monomers in the presence of poly(N-acetyliminoethylene) macroazoinitiators

New block copolymers with poly(N-acetyliminoethylene) and vinyl sequences were obtained by a two-step synthetic approach. In the first stage macroinitiators of poly(N-acetyliminoethylene) type, with azo groups inserted in the main chain, were prepared. They were latter used in the radical polymerization of some vinyl monomers [styrene, methacrylic acid, methyl methacrylate, butyl methacrylate, β-(N-carbazolyl)ethyl acrylate, β-(methacryloyfoxy)ethyl 3,5-dinitrobenzoate]. The resulting block copolymers were characterized by spectral methods, elemental analysis, gel permeation chromatography, and electron microscopy. The kinetic study of the thermal and photochemical decomposition of the synthesized macroazoinitiators, as well as the polymerization data, suggest a dependence of their initiating efficiency on the length of the poly(N-acetyliminoethylene) segments. © 1994 John Wiley & Sons, Inc.     

Influence of physical-chemical interactions on the thermal stability and surface properties of poly(vinyl chloride)-b-poly(hydroxypropyl acrylate)-b-poly(vinyl chloride) block copolymers

The synthesis of poly(vinyl chloride) (PVC) homopolymers and poly(vinyl chloride)-b-poly(hydroxypropyl acrylate)-b-poly(vinyl chloride) (PVC-b-PHPA-b-PVC) block copolymers via a single electron - degenerative transfer mediated living radical polymerisation was carried out on a pilot scale in industrial facilities. The thermal stability of the products was assessed conductimetrically. The block copolymers, that contained a low content of PHPA (below 12 wt.%), showed thermal stability that was approximately three times greater than that of conventional PVC. Inverse gas chromatography study of the copolymers surface showed that there was a decrease in the dispersive component and greater Lewis acidity and basicity constants were observed relative to those of PVC. The thermal stabilisation of PVC when in the presence of PHPA is explained by the interactions between its functional groups and the structures formed during the thermal degradation. The thermal stability and the surface properties of PVC-b-PHPA-b-PVC were strongly dependent on the molecular weight of the block copolymer. Lewis acid-base interaction parameters were determined and are interpreted as evidence of the PVC-b-PHPA-b-PVC compatibilising function in PVC-wood flour composites.     

Equation of state of copolymer melts: The poly(vinyl acetate)–polyethylene pair

The pressure—volume—temperature properties of a series of copolymers ranging in content from 18 to 40 wt % of vinyl acetate, and up to a maximum pressure of 1800 kg/cm² are studied. The results for the melt state can be satisfactorily fitted by the scaled equation of state, developed previously and applied to single-component systems and to mixtures. The dependence of the scaling parameters for the copolymers on composition deviates from that expected for a mixture, where volumes at elevated pressures can be predicted without further recourse to experiment. These differences are discussed in terms of the sequential structure of the copolymer chain and its series of interfaces between the two species.     

Poly(vinyl chloride)–poly(ethylene oxide) block copolymers: Synthesis and characterization

Poly(vinyl chloride)-poly(ethylene oxide) block copolymers have been synthesized in solution and emulsion. The polymers were made by first synthesizing macroazonitriles through the reaction of 4,4′-azobis-4-cyanovleryl chloride with hydroxy-terminated poly(ethylene oxide) of varying molecular weights. These macroazonitriles had molecular weights in the range of 3000–88,000 and degrees of polymerization from 5 to 24. Thermal decomposition of the azolinkages in the presence of vinyl chloride monomer yielded block copolymers containing form 2 to 20 wt % poly(ethylene oxide). The structures of the block copolymers were characterized by spectrometric, elemental and molecular weight analyses. The possibility of some graft polymerization occurring via free-radical extraction of a methylene hydrogen from the poly(ethylene oxide) was considered. Polymerization of vinyl chloride with an azonitrile initiator in the presence of a poly(ethylene oxide) yielded predominately homopolymer with some grafted poly(vinyl chloride).     

Viscometric and conductometric study of polyelectrolytes of low charge density in salt free aqueous solutions

Viscometric and conductometric measurements have been performed on dilute, salt free solutions of poly(vinyl alcohol) (PVA) and poly(vinyl alcohol, vinyl sulphate ester) copolymer salts in order to get information on transition from a neutral to charged macromolecules. With increasing linear charge density from a very low value to a moderate one a non linear dependence of polyelectrolyte effect on copolymer composition was observed. A comparison has shown that there is a close analogy between the expansion of polyanions and swelling of polyelectrolyte networks at comparable linear charge density range. Due to the intra- and inter-molecular mobile ionic bridges a considerable contraction was pointed out by viscometry for barium, magnesium and copper salts. However, the differences in properties of counterions of higher charge number indicates that in addition to the valency, there is a definite chemical effect, too. It has been revealed by the electric conductance measurements that the transition from a neutral to charged macromolecules could be a very complex one calling for a new and more detailed theoretical consideration of polyelectrolyte solutions.     

Temperature-responsive swelling and deswelling of the copolymers from vinyl ether of ethylene glycol and butyl vinyl ether

Linear and crosslinked copolymers of a vinyl ether of ethylene glycol (2-hydroxyethyl vinyl ether, ( 1 )) and butyl vinyl ether ( 2 ) are synthesized by α-irradiation polymerization. It is shown that the linear copolymers exhibit a phase separation phenomenon in dependence of the temperature due to the destruction of hydrogen bonds and the enhancement of hydrophobic interaction in aqueous solution. The processes of reversible swelling or shrinking upon temperature change are demonstrated for polymer networks.     

Grafting of Poly(Methyl Methacrylate) onto Poly(Vinyl Chloride) through Benzodithioate Groups

The synthesis and the characterization of poly (methyl methacrylate) (PMMA) grafted to poly(vinyl chloride) (PVC) through benzodithioate groups are studied. Unlike results generally obtained with conventional free-radical initiators for systems involving PVC and MMA, high conversions, and grafting efficiencies are achieved with azobis-isobutyronitrile. The paper describes the synthesis of p-vinylbenzodithioate-containing PVC and the dependence of the characteristics of PVC-g-PMMA on the composition of the reaction mixture. Characterization of the graft copolymers includes UV and IR spectroscopy, GPC, and microstructure analysis by removal of PMMA side chains by aminolysis of dithioesters groups. Intrinsic viscosity, glass transition temperature, and thermal sensitivity were investigated to confirm the grafted nature of the copolymer.     

Optically active polymers containing side-chain photochromic moieties. Synthesis and chiroptical properties of copolymers of trans-N(4-azobenzene)-maleimide with (−)-menthyl vinyl ether and (+)(S)-2-methylbutyl vinyl ether

The copolymers of trans-N(4-azobenzene)-maleimide (ABM) with optically active alkyl vinyl ethers, such as (?)-menthyl vinyl ether (MtVE) and (+)S-2-methylbutyl vinyl ether (MBVE), have been prepared either by direct copolymerization or by functionalization with trans-4-amino-azobenzene of the corresponding alternating copolymers of maleic anhydride with MtVE and MBVE. The chiroptical properties of the above copolymers have been studied by CD measurements. The induced optical activity on the side-chain trans-azobenzene moieties is discussed in terms of different conformational rigidity of the macromolecules.     

Synthesis and investigation of properties of repeatedly grafted copolymers (pemosors)

Repeatedly grafted copolymers (pemosors) were obtained by grafting one and the same or different vinyl monomers onto heterochain polymers in a radical reaction. As starting polymers films of polyethylene terephthalate and poly-ε-caproamide were used. Styrene and methyl methacrylate were the grafted vinyl monomers. It has been shown that pemosors could be formed in yields of 500–1000% (of the starting sample weight) by multiple grafting on vinyl polymer. Pemosors differ in appearance both from the starting polymers and the single-graft copolymers. Investigations of pemosor samples by electron microscope showed that the morphological structure of the surface was appreciably affected, the changes being more significant with increasing content of the grafted polymer. X-Ray studies and NMR data on pemosors showed that multiple grafting of vinyl monomers does not change the crystal structure of the starting polymers, affecting only the supermolecular structure of the outer layer. Pemosors are polymers of a new type, differing in their properties from the starting polymers and the single-graft copolymers. The grafting character and penetration depth of the grafted monomer depend on the packing compactness of the supermolecular structure of the polymeric base as well as on the chemical nature of the starting polymers and monomers. Pemosors possess considerable chemical resistance and withstand prolonged boiling in 40% alkali solution.     

Miscibility and morphologies of poly(arylene ether phenyl phosphine oxide/sulfone) copolymer/vinyl ester resin mixtures and their cured networks

Nonreactive bisphenol A‐based poly(arylene ether triphenyl phosphine oxide/diphenyl sulfone) statistical copolymers and a poly(arylene ether triphenyl phosphine oxide) homopolymer, each having a number‐average molecular weight of about 20 kg/mol, were synthesized and solution‐blended with a commercial dimethacrylate vinyl ester resin. Free‐radical cured systems produced morphologies that were a function of both the amount of phosphonyl groups and the weight percentage of the copolymers. For example, highly hydrogen‐bonded poly(arylene ether phenyl phosphine oxide) homopolymer/vinyl ester resin mixtures were homogeneous in all proportions both before and after the formation of networks. Copolymers containing low amounts (≤30 mol %) of the phosphonyl groups displayed phase separation either before or during cure. The phase‐separated cured materials generally had phase‐inverted morphologies, such as a continuous thermoplastic copolymer phase and a particulate, discontinuous vinyl ester network phase, except for systems containing a very low copolymer content. The resin modified with a copolymer containing 30 mol % phosphine oxide comonomer showed improved fracture toughness, suggesting the importance of both phase separation and good adhesion between the thermoplastic polymer and the crosslinked vinyl ester filler phase. The results suggested that the copolymers with high amounts of phosphine oxide should be good candidates for interphase sizing materials between a vinyl ester matrix and high‐modulus carbon fibers for advanced composite systems. Copolymers with low amounts of phosphonyl groups can produce tough, vinyl ester‐reinforced plastics. The char yield increases with the concentration of bisphenol A poly(arylene ether phosphine oxide) content, suggesting enhanced fire resistance. The incorporation of thermoplastic copolymers sustains a high glass‐transition temperature but does not significantly affect the thermal degradation onset temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2409–2421, 2000     

Synthesis of ABA‐triblock and star‐diblock copolymers with poly(2‐adamantyl vinyl ether) and poly(n‐butyl vinyl ether) segments: New thermoplastic elastomers composed solely of poly(vinyl ether) backbones

ABA‐type triblock copolymers and AB‐type star diblock copolymers with poly(2‐adamantyl vinyl ether) [poly(2‐AdVE)] hard outer segments and poly(n‐butyl vinyl ether) [poly(NBVE)] soft inner segments were synthesized by sequential living cationic copolymerization. Although both the two polymer segments were composed solely of poly(vinyl ether) backbones and hydrocarbon side chains, they were segregated into microphase‐separated structure, so that the block copolymers formed thermoplastic elastomers. Both the ABA‐type triblock copolymers and the AB‐type star diblock copolymers exhibited rubber elasticity over wide temperature range. For example, the ABA‐type triblock copolymers showed rubber elasticity from about ?53 °C to about 165 °C and the AB‐type star diblock copolymer did from about ?47 °C to 183 °C with a similar composition of poly(2‐AdVE) and poly(NBVE) segments in the dynamic mechanical analysis. The AB‐type star diblock copolymers exhibited higher tensile strength and elongation at break than the ABA‐type triblock copolymers. The thermal decomposition temperatures of both the block copolymers were as high as 321–331 °C, indicating their high thermal stability. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of poly(vinyl acetate)‐b‐polystyrene and poly(vinyl alcohol)‐b‐polystyrene copolymers by cobalt‐mediated radical polymerization

Well‐defined poly(vinyl acetate) macroinitiators, with the chains thus end‐capped by a cobalt complex, were synthesized by cobalt‐mediated radical polymerization and used to initiate styrene polymerization at 30 °C. Although the polymerization of the second block was not controlled, poly(vinyl acetate)‐b‐polystyrene copolymers were successfully prepared and converted into amphiphilic poly(vinyl alcohol)‐b‐polystyrene copolymers by the methanolysis of the ester functions of the poly(vinyl acetate) block. These poly(vinyl alcohol)‐b‐polystyrene copolymers self‐associated in water with the formation of nanocups, at least when the poly(vinyl alcohol) content was low enough. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 81–89, 2007