Structure–property relationship in polybutadiene–polyamide multiblock copolymers

Two kinds of aromatic–aliphatic polyamide oligomers were newly prepared by the reactant pairs of 3,4′-oxydianiline–adipic acid and 3,4′-oxydianiline–azelaic acid. These oligomers were then condensed separately with α, ω-polybutadienedicarboxylic acid giving two series of polybutadiene–polyamide multiblock copolymers. Properties of four series of polybutadiene–polyamide multiblock copolymers, whose polyamide blocks consisted of not only newly prepared polyamides but also previously synthesized aromatic polyamides derived from 4,4′-oxydianiline–isophthalic acid and 3,4′-oxydianiline–isophthalic acid, were investigated on the view point of structure-property relationship. A larger extent of the T_g depression of polybutadiene phase, and higher tensile strength and modulus were observed in the block copolymers having aromatic polyamides compared with those having aliphatic ones.     

乳液增稠技术的研究进展

增稠剂可以提高物系黏度,使物系保持均匀稳定的悬浮状态或乳浊状态,或形成凝胶。目前常用的增稠剂有纤维素及其衍生物类、聚丙烯酸及其共聚物类、非离子缔合型聚氨酯类等,对不同增稠剂特性的了解对于根据需要选择合适的增稠剂非常重要。主要以纤维素及其衍生物类、聚丙烯酸及其共聚物类、非离子缔合型聚氨酯类这三类主要的增稠剂为主,综述了乳液增稠的相关增稠机理以及研究应用技术。     

Tetraphenylethane iniferters: Polyurethane-polystyrene multiblock copolymers through “living” radical polymerization

Toluene diisocyanate-based polyurethane iniferters containing tetraphenyl-ethane groups in between polyurethane blocks were prepared by the reaction of isocyanate-terminated prepolymers and 1,1,2,2-tetraphenyl-1,2-ethanediol. When these iniferters were decomposed in the presence of styrene, polyurethane-polystyrene multiblock copolymers were obtained through a “living” radical mechanism. The effect of changing polyol on the T_g, thermal stability, and molecular weight of polyurethane iniferters as well as block copolymers was studied. The molecular weight of the block copolymers increased with increasing both polymerization time and conversion. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1551–1560, 1997     

Hydrogels based on polyurethane–polyacrylic acid multiblock copolymers via macroiniferter technique

Polyurethane (PU)–polyacrylic acid (PAAc) multiblock copolymers have been prepared via a macroiniferter technique, and were tested for living mechanism, thermal, and water swell of the cast films. It was found that molecular weight of the PU–PAAc block copolymers linearly increased while molecular weight distribution decreased with conversion. As the PAAc content increases, water swell of the cast films and crystalline melting temperature (T_m) of PU decreased while glass transition temperature of PU increased.     

Properties of crosslinked blends of pellethene and multiblock polyurethane containing poly(ethylene oxide) for biomaterials

A series of multiblock polyurethanes, containing various poly(ethylene oxide) (PEO; number‐average molecular weight = 400–3400) contents (0–80 wt %) and prepared from hexamethylene diisocyanate/PEO/poly(dimethylsiloxane) diol/polybutadiene diol/1,4‐butanediol, were used as modifying additives (30 wt %) to improve the properties of biomedical‐grade Pellethene. Different molecular weights of PEO were used to keep poly(ethylene glycol) at a fixed molar content, if possible, although the PEO content, related to the PEO block length in the multiblock polyurethanes, was varied from 0 to 80 wt %. The hydrophilic PEO component was introduced through the addition of PEO‐containing polyurethanes and dicumyl peroxide as a crosslinking agent in a Pellethene matrix. As the PEO content (PEO block length) increased, the hydrogen‐bonding fraction of the crosslinked Pellethene/multiblock polyurethane blends increased, and this indicated an increase in the phase separation with an increase in the PEO content in the crosslinked Pellethene/multiblock polyurethane blends. According to electron spectroscopy for chemical analysis, the ratio of ether carbon to alkyl carbon in the crosslinked Pellethene/multiblock polyurethane blends increased remarkably with increasing PEO content. The water contact angle of the crosslinked Pellethene/multiblock polyurethane blend film surfaces decreased with increasing PEO content. The water absorption and mechanical properties (tensile modulus, strength, and elongation at break) of the crosslinked Pellethene/multiblock polyurethane blend films increased with increasing PEO content. The platelet adhesion on the crosslinked Pellethene/multiblock polyurethane blend film surfaces decreased significantly with increasing PEO content. These results suggest that crosslinked Pellethene/multiblock polyurethane blends containing the hydrophilic component PEO may have potential for biomaterials that come into direct contact with blood. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2348–2357, 2004     

Synthesis and properties of multiblock copolymers based on polydimethylsiloxane and piperazine-aromatic polyamides

Polydimethylsiloxane (PDMS)–polyamide multiblock copolymers were synthesized by three different methods, i.e., two-step low-temperature solution polycondensation, one-step solution polycondensation, and interfacial polycondensation. In the two-step method, α,ω-diacid chlorideterminated polyamide oligomers were prepared from trans-2,5-dimethylpiperazine (DMP) and terepthaloyl chloride (TPC) or isophthaloyl chloride (IPC) in chloroform in the presence of triethylamine, which in turn were subjected to reaction with α,ω-bis (3-aminopropyl) polydimethylsiloxane (PDMS–diamine) in the same solvent to from multiblock copolymers. In the one-step method, the reaction components, DMP, TPC (or IPC), and PDMS–diamine, were reacted altogether in chloroform in the presence of triethylamine. In the interfacial method, the reaction components were also reacted altogether in an aqueous sodium hydroxide–chloroform two-phase system. These polycondensations afforded the multiblock copolymers having inherent viscosities of 0.1–1.3 dL g^?1 in m-cresol. The PDMS–polyamide multiblock copolymers dissolved in formic acid and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), and transparent, ductile, and elastomeric films were obtained by casting from the HFIP solutions. The films of the multiblock copolymers prepared by three different methods exhibited similar properties by means of thermal analysis and tensile measurements. In the multiblock copolymers, the tensile strength and modulus of the films decreased with increasing the PDMS content, whereas the elongation at break increased.     

Waterborne anionomeric polyurethane–ureas from functionalized fluoropolyethers

A family of anionomeric segmented polyurethane–ureas made from α‐ω dimethylol‐terminated perfluoropolyethers (M_n = 1000–2000), isophorone diisocyanate, dimethylol propionic acid, and ethylenediamine was obtained in form of stable aqueous dispersions. The dispersions were characterized by viscometry and dynamic laser light scattering. The main compositive parameters explored were the amount of COOH groups and the length of the fluorinated macromer. The new polyurethane–ureas were characterized by dynamic mechanical analysis obtaining information on modulus, thermal transition, and phase segregation. Surface properties and chemical resistance were estimated through measurements of static contact angles and spot tests with different solvents. Although surface hydrophobicity was not affected by composition, water‐sorption behavior was sensitive to the ionic character (COOH level) of the polymer. Diffusion and permeability coefficients of polymer films, having different carboxyl contents, were estimated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 136–144, 2004     

Facile synthesis of multiblock copolymers composed of poly(tetramethylene oxide) and polystyrene using living free-radical polymerization macroinitiator

A facile synthetic strategy for well-defined multiblock copolymers utilizing ‘living’ free-radical polymerization macroinitiator has been presented. Polyurethane composed of alkoxyamine initiating units and poly(tetramethylene oxide) (PTMO) segments was prepared by polyaddition of tolylene 2,4-diisocyanate terminated PTMO with an alkoxyamine-based diol. Polymerization of styrene with the polyurethane macroinitiator was carried out under nitroxide-mediated free-radical polymerization (NMRP) condition. GPC, NMR, and IR data revealed that the polymerization was accurately controlled and well-defined polystyrene chains were inserted in the main chain of macroinitiator to give the poly(tetramethylene oxide)-b-polystyrene multiblock copolymers. The synthesized multiblock copolymers were characterized by tensile test, differential scanning calorimetry, and dynamic mechanical analysis. Mechanical properties of the multiblock copolymers can be tuned by the sufficient molecular weight control of PS chains. Soft segment of PTMO and hard segment of PS were apparently compatible due to the multiblock structure of low molecular weight segments and polar urethane groups.     

Effect of multiblock copolymers in polymer blends

The use of multiblock copolymers for the compatibilization of immiscible polymer blends is controversially discussed in the literature. Investigations have been carried out to estimate the effect of multiblock copolymers containing segments of a liquid crystalline polyester (LCP) and polysulfone (PSU) segments in blends of the based homopolymers. One goal was to determine whether multiblock copolymers provide an opportunity for compatibilizing PSU/LCP blends. By using PSU/LCP multiblock copolymers with different molecular weights of the blocks in the appropriate binary, solution-casted blends, it was shown that the interpenetration of the polysulfone phase of the block copolymer and the PSU matrix leads to an improved miscibility of the blend. This effect is retained in ternary blends of PSU, LCP, and the multiblock copolymer, assuming a certain critical molecular weight of the multiblock copolymer segments. In addition, some mechanical characteristics of PSU/LCP melt blends such as the E-modulus and fracture strength are improved by adding long-segmented multiblock copolymers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2293–2309, 1997     

The kinetics of dithiocarbamate-mediated polyurethane-block-poly(methyl methacrylate) polymers

One important advantage offered by polymeric iniferters is the possibility that polycondensation polymers could be further reacted with vinyl monomers to produce novel block copolymers with interesting properties. The objective of this work was the kinetic investigation of polyurethane-block-poly(methyl methacrylate) (PU-b-PMMA) using dithiocarbamate (DC)-based polyurethane macroiniferter (PUMI) at different concentrations. It is shown that the copolymerization reactions followed the first order dependency. A linear increase of molecular weight with monomer conversion demonstrated that the copolymerization followed the mechanism of controlled radical polymerization. The rate of polymerization (R_p) at specific reaction time increased as the PUMI concentration increased from 0.34 × 10⁻³ mol/L to 2.74 × 10⁻³ mol/L, pass through a maxima, and decreased as PUMI concentration was increased beyond 2.74 × 10⁻³ mol/L. The thermogravimetric analysis showed that both PUMI and PU-b-PMMA degraded in three distinctive stages but the PU-b-PMMA is thermally more stable than the PUMI especially at lower temperatures. Thus, a combination of polycondensation and free radical photopolymerization methods, as demonstrated in this study, could be used to synthesize polyurethane-based block copolymers with tailored chain lengths of different blocks suitable for biomedical applications.     

Chain architecture and molecular self-organization of polyurethanes: Perspectives for thermoplastic elastomers

Segmented polyurethanes with a regular chain architecture exhibit very specific self-organizing properties, often leading to multiphase systems with special phase structures. The study of a series of relatively stiff, monodisperse polyurethane model compounds of various molecularly engineered structures and also multiblock copolymers consisting of an alternating sequence of highly flexible polyether and the above polyurethane segment has shown that extended chain crystallization and chain folding of hard segments and thus the size, shape and ordering of the hard domains can be created and rearranged at will. The molecular design, which can also be applied to graft copolymers, predetermines the possibilities of supramolecular organization. These thermoplastic elastomers exhibit very special properties which correlate sysmatically with the supramolecular structure.     

Multi-block copolymer dispersions through polyurethane macroiniferters

Summary Tetraphenylethane-based polyurethane macroiniferter has been used to prepare polyurethane-polymethacrylic acid multi-block copolymers. These block copolymers have been converted into corresponding anionomers by treating them with triethylamine. Dispersions have been prepared by adding water into dimethylformamide solutions of block copolymers and their anionomers. Particle size and viscosity of the dispersions have been determined. The films obtained from the dispersions have been characterized by mechanical and dynamic mechanical analyses. Received: 18 March 1998/Revised version: 13 April 1998/Accepted: 16 April 1998     

Synthesis and characterization of perfectly alternating polycarbonate‐polydimethylsiloxane multiblock copolymers possessing controlled block lengths

An array of perfectly alternating polycarbonate‐polydimethylsiloxane (PC‐PDMS) multiblock copolymers possessing systematic variations in block molecular weights were successfully produced by coupling preformed PC and PDMS telechelic oligomers using hydrosilylation. Based on gel permeation chromatography results, the multiblock copolymers were essentially void of the oligomeric precursors. Despite the relatively large difference in solubility parameter between PC and PDMS, the multiblock copolymers exhibited significant partial miscibility between the two phases. As expected, the degree of partial miscibility was dependent on the molecular weight of the blocks with the extent of partial miscibility increasing with decreasing block molecular weights. Morphological characterization using small angle X‐ray scattering showed that, at a given PC block molecular weight, the uniformity of the two phase morphology increased with increasing PDMS block molecular weight, which is consistent with a decrease in the extent of phase mixing with increasing PDMS block molecular weight. POLYM. ENG. SCI., 54:1648–1663, 2014. © 2013 Society of Plastics Engineers     

Anionic bulk polymerization to synthesize styrene–isoprene diblock and multiblock copolymers by reactive extrusion

In this study, styrene–isoprene diblock and multiblock copolymers were synthesized with n‐butyllithium as the initiator, in an intermeshing, corotating twin‐screw extruder. The diameter (D) of this extruder was 36 mm, and the ratio of length/diameter was 56. The weight content of polyisoprene in these copolymers was above 50% although in the past studies it had not been possible to accomplish levels higher than 30%. Gel permeation chromatography results of samples and their degraded products show that there is only one long block polystyrene in the diblock copolymer chains; while in the multiblock copolymer molecules, there is a long block and large numbers of small blocks. Dynamic mechanical analysis and transmission electron microscopy show that the two phases in the diblock copolymer are completely incompatible, leading to sharp phase separation. In the multiblock copolymer, the two phases are partly compatible without an obvious phase boundary. The successful syntheses of styrene/isoprene diblock and multiblock copolymers with high‐isoprene contents provide a novel method to synthesize polystyrene rubbers and styrene–diene–styrene thermoplastic elastomers. Traditionally, these products were mainly synthesized by solution polymerization. The present work in this article provides the possibility to synthesize them with very little or no solvent using bulk polymerization. This method fits the environmentally friendly trend to use low amounts of carbon while allowing commercial profitability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39429.     

Nano-structure phosphorus-containing polyurethane dispersions: synthesis and crosslinking with melamine formaldehyde resin

Nano-particle-size phosphated polyurethane dispersions were synthesised from phosphorus-containing macroglycol, bis (hydroxymethyl) propionic acid and methylene-bis-(4-isocyanatocyclohexane) (H₁₂MDI). After the carboxylic acid groups of the phosphated polyurethane were neutralised by suitable bases, water was added to form the phosphated polyurethane dispersion. Chain flexibility affected particle-size reduction because flexible particles are more deformable in a shear field. During phase inversion the dispersed phase can more easily be broken into smaller particles. Depending on the number of hydrophilic groups present, the dispersion can be obtained in a very finely divided form, so that it practically has the appearance of a solution.Crosslinking of the dispersions with melamine showed that hexamethoxymethyl melamine does not self-condense during the curing and co-condensation was predominant. It was further shown that the cure response of the polyurethane dispersions was affected by the nature of the neutralising amine. Triethanolamine neutralised dispersions gave very poor cure response compared with triethylamine due to the low-volatility and the tendency to enter side reaction with the melamine.     

Preparation and colloidal properties of an aqueous acetic acid lignin containing polyurethane surfactant

Aqueous acetic acid lignin containing polyurethane (ALPU) surfactants were prepared by the replacement of some hydrophobic poly(caprolactone diol) with different concentrations of multifunctional acetic acid lignin (AL), and with dimethylol propionic acid as the hydrophilic segment. The infrared spectra, together with thermogravimetric analysis, demonstrated the presence of AL in the polyurethane (PU) chains. In addition, the effects of the AL concentration on the particle size, morphology, rheological behavior, and surface activity of the dispersions were investigated. The ALPU particles displayed a spherical morphology. With increasing AL concentration from 0 to 10 wt %, the particle size increased from 36 to 260 nm, and the unimodal distribution was detected for ALPU₁₀ with a 10 wt % AL addition. The viscosity and shear‐thinning behavior of the ALPU dispersions decreased, and the lowest surface tension and critical micelle concentration (cmc) were detected for ALPU₁₀. However, when the AL concentration was 15 wt % (ALPU₁₅), the surface tension and cmc increased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1855–1862, 2013     

Aqueous polyurethane dispersions derived from polycarbonatediols and Di(4‐isocyanatocyclohexyl)methane

Aqueous polyurethane dispersions derived from various polycarbonatediols, di(4‐isocyanatocyclohexyl)methane (HMDI), and various carboxylic diols, including dimethylol propionic acid (DMPA), dimethylol butyric acid (DMBA), and a carboxylic polycaprolactonediol, were prepared by a method in which the dispersing procedure was modified to enhance the molecular weight. The molecular weight, particle size, tensile properties, thermal properties, and dynamic mechanical properties of the polyurethane dispersions were investigated. The dynamic mechanical property data indicate that these polyurethane dispersions can exhibit higher temperature resistance when compared with those derived from isophorone diisocyanate (IPDI). POLYM. ENG. SCI. 46:588–593, 2006. © 2006 Society of Plastics Engineers     

Starlike Nylon 6/polyurethane block copolymers by reaction injection‐molding process (RIM)

Starlike block copolymers of Nylon‐6 and polyurethane were synthesized using ε‐caprolactam as a monomer, caprolactam magnesium bromide as a catalyst, and a star prepolymer of polyurethane. These copolymers were compared with the linear block copolymers of Nylon‐6 and polyurethane. Such copolymers were obtained using the reaction injection‐molding process (RIM) of ε‐caprolactam at different contents of polyurethane (5–30 wt %). In increasing the content of the soft phase, in FTIR, a displacement was observed in the band at 1637 cm^?1, assigned to the amide I of the Nylon 6, to a higher wavenumber. This suggests a bigger interaction between the urethane group of the polyurethane and the amide group of the Nylon 6. Star block copolymers showed better mechanical properties compared with the linear ones. This behavior is attributed to the higher crystallinity and ramifications present in the materials. The structure and the thermal properties of the copolymers were studied using different techniques such as DSC, WAXS, DMA, and SEM. A decrease in the crystallinity when increasing the soft phase was also observed. Finally, physical tensile, impact, and hardness tests of the copolymers were carried out. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2483–2494, 2001     

Aqueous polyurethane dispersions derived from polycarbonatediols

Aqueous polyurethane dispersions derived from polycarbonatediols, isophorone diisocyanate, and carboxylic diols including dimethylol propionic acid and dimethylol butyric acid were prepared. The effect of dispersing procedure is investigated by FT IR, GPC, and the tensile film properties. The polyurethane dispersions prepared by a standard procedure exhibit lower molecular weights due to the overhydrolysis of the NCO groups. The polyurethane dispersions prepared by a modified procedure exhibit significantly higher molecular weights due to more effective chain extension, and their cast films exhibit higher tensile strength. The particle size, tensile properties, thermal properties, and dynamic mechanical properties are investigated. The chemical structure of the polycarbonatediols seems to affect the tensile strength. The glass transition temperature of the soft segments, T_g(S), of the polyurethane dispersions can be seem from the DSC and DMA data. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1723–1729, 2004     

Effect of composition on aqueous polyurethane dispersions derived from polycarbonatediols

Aqueous polyurethane dispersions derived from isophorone diisocyanate, various polycarbonatediols of different molecular weights, and dimethylol butyric acid were prepared by a dispersing procedure modified to enhance molecular weight. Particle size, average molecular weight, and tensile properties were determined. The molar ratio of reactants affected the properties of the polyurethane dispersions significantly, with the trends described as the effects of their ionic group and polycarbonatediol soft‐segment contents. The molecular weight of the polycarbonatediols also significantly affected the particle size of the aqueous polyurethane dispersions and the film properties. As the molecular weight of the polycarbonatediols decreased, the particle size of the aqueous polyurethane dispersions decreased, and the moduli of the cast films increased, as expected. However, the tensile strength of the cast films decreased as the molecular weight of the polycarbonatediols decreased because of the decrease in elongation at break. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4419–4424, 2006