Phase behavior of aqueous systems containing block copolymers of poly(ethylene oxide) and poly(propylene oxide)

Phase behavior of aqueous systems containing block copolymers of poly(ethylene oxide (PEO) and poly(propylene oxide) (PPO) was evaluated by building up temperature-concentration phase diagrams. We have studied bifunctional triblock copolymers (HO-PEO-PPO-PEO-OH) and monofunctional diblock copolymers (R-PEO-PPO-OH and R-PPO-PEO-OH, where R length is linear C₄ and C_12–14). The cloud points of the polymer solutions depended on EO/PO ratio, polarity, R length and position of the hydrophilic and hydrophobic segments along the molecule. Such factors influence on the solutions behavior was also analyzed in terms of critical micelle concentration (CMC), which was obtained from surface tension vs. concentration plots. Salts (NaCl and KCl) added into the polymer solutions change the solvent polarity decreasing the cloud points. On the other hand, the cloud points of the polymer solutions increased as a hydrotrope (sodium p-toluenesulfonate) was added. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1767–1772, 1997     

First results of small and wide angle X-ray scattering of poly(ethylene oxide)/poly(methyl methacrylate) binary blends

Some preliminary small and wide angle X-ray scattering results are reported from isothermally crystallized samples of poly(ethylene oxide)/(methyl methacrylate) binary blends.     

Small-angle light scattering studies of macrophase separation in segmented polyurethane block copolymers

Quantitative small-angle light scattering (SALS) analysis is carried out on two similar segmented polyurethane block copolymers. The polyurethane prepared from toluene diisocyanate, is optically transparent, while a polyurethane prepared using the same soft segment, but with 4-4′ diphenyl methane diisocyanate, scatters light appreciably. SALS investigation of the latter sample shows clearly that the scattering arises from the presence of long-range density fluctuations. Analysis of the density fluctuations is accomplished with the Debye-Bueche theory for random two-phase systems, incorporating a correction for the effects of multiple scattering. Application of this procedure leads to a correlation length of 4200 nm; corresponding well with the structure observed in optical photo-micrographs. The occurrence of phase separation during polymerization is discussed as a possible origin for the observed macrophase structure.     

Phase behaviour in poly(ethylene oxide-b-t-butyl methacrylate) block copolymers

The lamellar thickness of the poly(ethylene oxide)-poly(t-butyl methacrylate) (PEO-PTBMA) diblock copolymer system, obtained by differential scanning calorimetry and small angle X-ray scattering investigations, is correlated with the degree of polymerization of the amorphous (PTBMA) and crystallizable (PEO) sequences. The non-equilibrium exponents obtained immediately after bulk crystallization are different to those from extrapolated equilibrium results. Within the experimental standard deviations, the theoretical predictions of DiMarzio et al. and of Whitmore and Noolandi could be confirmed. The molecular weights of PEO and PTBMA ranged from 250 to 21000 g mol⁻¹ and from 1500 to 17000 g mol⁻¹, respectively. Both the equilibrium lamellar thickness l and the PEO domain size d_PEO increase with increasing PEO and decreasing PTBMA degrees of polymerization Z according to d_PEO l Z^0.97±0.08_EOZ^{−(0.53±0.19)}_TBMA.     

Synthesis and properties of hydrophilic segmented block copolymers based on poly(ethylene oxide)‐ran‐poly(propylene oxide)

The present article discusses the synthesis and various properties of segmented block copolymers with random copolymer segments of poly(ethylene oxide) and poly(propylene oxide) (PEO‐r‐PPO) together with monodisperse amide segments. The PEO‐r‐PPO contained 25 wt % PPO units and the segment presented a molecular weight of 2500 g/mol. The synthesized copolymers were analyzed by differential scanning calorimetry, Fourier transform infra‐red spectroscopy, atomic force microscopy and dynamic mechanical thermal analysis. In addition, the hydrophilicity and the contact angles (CAs) were studied. The PEO‐r‐PPO segments displayed a single low glass transition temperature, as well as a low PEO crystallinity and melting temperature, which gave enhanced low‐temperature properties of the copolymer. The water absorption values remained high. In comparison to mixtures of PEO/PPO segments, the random dispersion of PPO units in the PEO segments was more effective in reducing the PEO crystallinity and melting temperature, without affecting the hydrophilicity. Increasing the polyether segment length with terephthalic groups from 2500 to 10,000 g/mol increased the hydrophilicity and the room temperature elasticity. Furthermore, the CAs were found to be low 22–39° and changed with the crosslink density. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117:1394–1404, 2010     

Preparation and characterizations of interpenetrating polymer network hydrogels of poly(ethylene oxide) and poly(methyl methacrylate)

Interpenetrating polymer network (IPN) hydrogels based on poly(ethylene oxide) and poly(methyl methacrylate) were prepared by radical polymerization using 2,2‐dimethyl‐2‐phenylacetophenone and ethylene glycol dimethacrylate as initiators and crosslinkers, respectively. The IPN hydrogels were analyzed for sorption behavior at 25°C and at a relative humidity of 95% using dynamic vapor sorption. The IPN hydrogels exhibited a relatively high equilibrium water content in the range of 13–68%. The state of water in the swollen IPN hydrogels was investigated using differential scanning calorimetry. The free water in the hydrogels increased as the hydrophilic content increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 258–262, 2003     

Probing the structure of polymer blends by vibrational spectroscopy: the case of poly(ethylene oxide) and poly(methyl methacrylate) blends

The blends of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) are prepared in the form of thin films from solution casting. The Fourier transform infrared spectra of the blends are recorded in the spectral range 400–4000 cm^?1. The spectra are analysed using various recent techniques of vibrational spectroscopy. It is concluded that upon blending PEO takes preferentially a planar zig-zag structure. Furthermore the intermolecular interactions between the molecules of PEO and PMMA in blends are very weak and their compatibility as blends is more ‘physical’ than ‘chemical’. Further, on the basis of the atomic charges transferred from model molecules it is seen that the blending is preferred with isotactic PMMA when compared to syndiotactic PMMA.     

Casting solvent effect on crystallization behavior and morphology of poly(ethylene oxide)/poly(methyl methacrylate)

Poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends were prepared by casting from either chloroform or benzene solvents. After casting from solvents, all samples used in this study were preheated to 100°C and held for 10 min. Then, the solvent effect on the crystallization behavior and thermodynamic properties were studied by differential scanning calorimeter (DSC). Also, the morphology of spherulite of casting film was studied by polarized optical microscope. From the DSC and polarizing optical microscopy (POM) results, it was found that PEO/PMMA was miscible in the molten state no matter which casting solvent was used. However, the crystallization of PEO in the chloroform‐cast blend was more easily suppressed than it was in the benzene‐cast blend. Relatively, the chloroform‐cast blend showed the greater melting‐point depressing of PEO crystals. Also, the spherulite of chloroform‐cast film showed a coarser birefringence. It was supposed that the chloroform‐cast blend had more homogeneous morphology. It is fair to say that polymer blends, cast from solvent, are not necessarily in equilibrium. However, the benzene‐cast blends still were not in equilibrium even after preheating at 100°C for 10 min. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1627–1636, 2000     

Spherulitic crystallization in blends of poly(ethylene oxide) and poly(methyl methacrylate)

The crystallization kinetics of binary blends of poly(ethylene oxide) and poly(methyl methacrylate) were investigated. The isothermal spherulitic growth rates were measured by means of a polarized light microscope. The temperature and composition dependence on the growth rates have been analysed. The temperature range studied was from 44° to 58°C. The introduction of poly(methyl methacrylate) into poly(ethylene oxide) resulted in a reduction of the spherulitic growth rate as the proportion of poly(methyl methacrylate) was increased from zero to 40% by weight. Results have been analysed using the theoretical equations of Boon and Azcue for the growth rate of polymer-diluent mixtures. The experimental results are in good agreement with this equation. The temperature coefficient is negative as is the case in the crystallization of bulk homopolymers.     

A new synthetic approach to asymmetric amphiphilic ABA′ block copolymers by ATRP and click reactions

Well‐defined asymmetric amphiphilic ABA′ block copolymers composed of poly(ethylene oxide) monomethylene ether (MPEO) with different molecular weights as A or A′ block and poly(styrene) (PS) as B block were synthesized by the combination of atom transfer radical polymerization (ATRP) and click reactions. First, bromine‐terminated diblock copolymer poly(ethylene oxide) monomethylene ether‐block‐poly(styrene) (MPEO‐PS‐Br) was prepared by ATRP of styrene initiated with macroinitiator MPEO‐Br, which was prepared from the esterification of MPEO and 2‐bromoisobutyryl bromide. Then, the azido‐terminated diblock copolymers MPEO‐PS‐N₃ were prepared through the bromine substitution reaction with sodium azide. Propargyl‐terminated MPEO with a different molecular weight was prepared under the basic condition from propargyl alcohol and p‐toluenesulfonyl‐terminated MPEO, which was prepared through the esterification of MPEO and p‐toluenesulfochloride using pyridine as solvent. Asymmetric amphiphilic ABA′ block copolymers, with a wide range of number–average molecular weights from 1.92 × 10⁴ to 2.47 × 10⁴ and a narrow polydispersity from 1.03 to 1.05, were synthesized via a click reaction of the azido‐terminated diblock copolymers and the propargyl‐terminated MPEO in the presence of CuBr and 1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) catalyst system. The structures of these ABA′ block copolymers and corresponding precursors were characterized by NMR, IR, and GPC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of composition and molecular mass on the morphology,crystallization and melting behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends

Results are reported on the influence of composition and molecular mass of components on the isothermal growth rate of spherulites, on the overall kinetic rate constant, on the primary nucleation and on the thermal behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends. The growth rate of PEO spherulites as well as the observed equilibrium melting temperatures decrease, for a given T_c or ΔT, with the increase of PMMA content.Such observations are interpreted by assuming that the polymers are compatible in the undercooled melt, at least in the range of crystallization temperatures investigated. Thermodynamic quantities such as the surface free energy of folding σ_e and the Flory-Huggins parameter χ₁₂ have been obtained by studying the dependence of the radial growth rate G and of the overall kinetic rate constant K from temperature and composition and the dependence of the equilibrium melting temperature depression ΔT_m upon composition, respectively.     

Synthesis of block copolymers via redox polymerization

Polymerization and copolymerization of vinyl monomers such as acrylamide, acrylonitrile, vinyl acetate, and acrylic acid with a redox system of Ce(IV) and organic reducing agents containing hydroxy groups were studied. The reducing compounds were poly(ethylene glycol)s, halogen‐containing polyols, and depolymerization products of poly(ethylene terephthalate). Copolymers of poly(ethylene glycol)s‐b‐polyacrylonitrile, poly(ethylene glycol)s‐b‐poly(acrylonitrile‐co‐vinyl acetate), poly(ethylene glycol)s‐b‐polyacrylamide, poly(ethylene glycol)s‐b‐poly(acrylamide‐co‐vinyl acetate), poly(1‐chloromethyl ethylene glycol)‐bpoly(acrylonitrile‐co‐vinyl acetate), and bis[poly(ethylene glycol terephthalate)]‐b‐poly(acrylonitrile‐co‐vinyl acetate) were produced. The yield of acrylamide polymerization and the molecular weight of the copolymer increased considerably if about 4% vinyl acetate was added into the acrylamide monomer. However, the molecular weight of the copolymer was decreased when 4% vinyl acetate was added into the acrylonitrile monomer. Physical properties such as solubility, water absorption, resistance to UV light, and viscosities of the copolymers were studied and their possible uses are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1385–1395, 1999     

含聚乙二醇的嵌段共聚物的合成及自组装研究进展

综述了通过活性自由基聚合如原子转移自由基聚合（ATRP）、氮氧稳定自由基聚合（NMP）、可逆加成断裂链转移聚合（RAFT）等方法合成含聚乙二醇（PEG）的嵌段共聚物的研究进展,并对含PEG类嵌段共聚物在溶液中的自组装技术和在药物载体、介孔材料以及碳纳米管中的应用进行了归纳,指出含PEG的嵌段共聚物可以自组装成多种形貌,直接影响材料的性能和应用,所以这些结构有潜在的应用价值和应用前景,并且合成新的含PEG的嵌段共聚物和开发具有新型结构、形貌可控的自组装体以及新的应用领域是今后的一个热点问题,具有重要的科学研究意义和实际应用价值。     

Synthesis and characterization of poly(dimethyl siloxane) containing poly(vinyl pyrrolidinone) block copolymers

ABA‐type block copolymers containing segments of poly(dimethyl siloxane) and poly(vinyl pyrrolidinone) were synthesized. Dihydroxyl‐terminated poly(dimethyl siloxane) was reacted with isophorone diisocyanate and then with t‐butyl hydroperoxide to obtain macroinitiators having siloxane units. The peroxidic diradical macroinitiators were used to polymerize vinyl pyrrolidinone monomer to synthesize ABA‐type block copolymers. By use of physicochemical methods, the structure was confirmed, and its characterization was accomplished. Mechanical and thermal characterizations of copolymers were made by stress–strain tests and differential scanning calorimetric measurements. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1915–1922, 1999     

Towards a one‐pot synthesis of a polystyrene–PMMA block copolymer via atom‐transfer radical polymerization

The solution atom‐transfer radical copolymerization of styrene and methyl methacrylate in butyl acetate at 110 °C in the presence of Cu(II) bromide and 2,2′‐bipyride was investigated. Polystyrene was polymerized by atom‐transfer radical polymerization using benzyl bromide as initiator and MMA was then added to the system. Block copolymers were formed when MMA was added at ≤90% styrene conversion. Molecular weight distributions (M_w/M_n) of the block copolymers were ≤1.5. The possibility of end‐capping the polystyrene precursor as a means of improving its initiating efficiency towards MMA was also investigated but did not improve the system. © 2002 Society of Chemical Industry     

Hyperbranched–linear–hyperbranched ABA‐type block copolymers based on poly(ethylene oxide) and polyglycerol

BACKGROUND: Until recently, hyperbranched polymers were thought to be ill‐defined materials that were not useful as building blocks for well‐defined complex polymer architectures. It is a current challenge to develop strategies that offer rapid access to well‐defined hyperbranched block copolymers. RESULTS: A convenient three‐step protocol for the synthesis of double‐hydrophilic hyperbranched–linear–hyperbranched ABA‐type triblock copolymers based on poly(ethylene oxide) (PEO) and hyperbranched polyglycerol (hbPG) is presented. The Bola‐type polymers exhibiting an aliphatic polyether structure were prepared from a linear (lin) linPG‐b‐PEO‐b‐linPG precursor triblock. The materials exhibit low polydispersities (M_w/M_n) in the range 1.19–1.45. The molecular weights of the block copolymers range from 6300 to 26 200 g mol^?1, varying in the length of both the linear PEO chain as well as the hbPG segments. Detailed characterization of the thermal properties using differential scanning calorimetry demonstrates nanophase segregation of the blocks. CONCLUSION: The first example of well‐defined ABA hyperbranched–linear–hyperbranched triblock copolymers with PEO middle block and hbPG A‐blocks is presented. The biocompatible nature of the aliphatic polyether blocks renders these materials interesting for biomedical purposes. These new materials are also intriguing with respect to their supramolecular order and biomineralization properties. Copyright © 2009 Society of Chemical Industry     

自由基聚合制备甲基丙烯酸甲酯-苯乙烯嵌段共聚物

以偶氮二异丁腈为引发剂,乙二硫醇（EDT）为链转移剂进行甲基丙烯酸甲酯（MMA）的自由基聚合,得到了含有残余巯基的聚甲基丙烯酸甲酯大分子链转移剂（HS-PMMA）,继而以HS-PMMA作为大分子链转移剂进行苯乙烯的自由基聚合,采用普通自由基聚合方法合成了结构可以设计的嵌段共聚物。     

甲基丙烯酸丁酯-PEG梳形共聚物的合成与表征

以偶氮双异丁腈(AIBN)为引发剂,四氢呋喃为溶剂,采用甲基丙烯酸正丁酯(BMA)与聚乙二醇单甲醚甲基丙烯酸酯(POEM)共聚制备了支链上含聚乙二醇(PEG)的梳形共聚物。采用1H-NMR、DSC和表面接触角等方法研究了梳形共聚物的结构与性能。结果表明,聚合物中两结构单元的含量与单体投料比中的含量基本一致;投料比对聚合物的结构和性能有较为显著的影响;梳形聚合物的熔点、焓值及静态接触角随着共聚物中BMA含量的升高而升高。     

Preparation and characterization of polystyrene–poly(ethylene oxide) amphiphilic block copolymers via atom transfer radical polymerization: Potential application as paper coating materials

Poly(ethylene oxide) (PEO) monochloro macroinitiators or PEO telechelic macroinitiators (Cl‐PEO‐Cl) were prepared from monohydroxyfunctional or dihydroxyfunctional PEO and 2‐chloro propionyl chloride. These macroinitiators were applied to the atom transfer radical polymerization of styrene (S). The polymerization was carried out in bulk at 140°C and catalyzed by Copper(I) chloride (CuCl) in the presence of 2,2′‐bipyridine (bipy) ligand (CuCl/bipy). The amphiphilic copolymers were either A‐B diblock or A‐B‐A triblock type, where A block is polystyrene (PS) and B block is PEO. The living nature of the polymerizations leads to block copolymers with narrow molecular weight distribution (1.072 < M_w/M_n < 1.392) for most of the macroinitiators synthesized. The macroinitiator itself and the corresponding block copolymers were characterized by FTIR, ¹H NMR, and SEC analysis. By adjusting the content of the PEO blocks it was possible to prepare water‐soluble/dispersible block copolymers. The obtained block copolymers were used to control paper surface characteristics by surface treatment with small amount of chemicals. The printability of the treated paper was evaluated with polarity factors, liquid absorption measurements, and felt pen tests. The adsorption of such copolymers at the solid/liquid interface is relevant to the wetting and spreading of liquids on hydrophobic/hydrophilic surfaces. From our study, it is observed that the chain length of the hydrophilic block and the amount of hydrophobic block play an important role in modification of the paper surface. Among all of block copolymers synthesized, the PS‐b‐PEO‐b‐PS containing 10 wt % PS was found to retard water absorption considerably. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4304–4313, 2006     

Synthesis and thermal behavior of triblock copolymers from L-lactide and ethylene glycol with long center PEG block

In this study, poly(L -lactide)–poly (ethylene glycol) (PLLA–PEG) ABA triblock copolymers with the PEG mole fraction ranging from 27 to 57% have been synthesized, and their thermal properties were investigated. Differential scanning calorimetric thermograms of copolymers obtained from specimens dissolved in CH₂Cl₂ solution and precipitated with hexane exhibit no crystallization exotherms, but those cast from CHCl₃ solution show some crystallinity. Water absorption depended on the PEG content of copolymers; thus, with a PEG mole fraction of 57, the water absorption was 82%. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1949–1954, 1998