Synthesis and characterization of oxymethylene-linked 2-vinylpyridine/oxyethylene multiblock copolymers

Oxymethylene-linked (2-vinylpyridine-oxyethylene) multiblock copolymers were prepared by coupling telechelic α,ω-dihydroxypoly(2-vinylpyridine) (THPVP) and poly(ethylene oxide) (PEO), using dichloromethane as coupling agent and KOH as catalyst. THPVP was synthesized by polymerization of 2-vinylpyridine in tetrahydrofuran/benzene using 1-methylnaphthyllithium as anionic initiator, followed by capping with ethylene oxide and termination by methanol. The effects of charging weight ratio of PEO/THPVP, copolymerization time and molecular weight of PEO or THPVP on the copolymerization were studied. The copolymers were characterized by IR, ¹H NMR, membrane osmometry, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC).     

吸水性热塑性橡胶——氧乙烯——氧丙烯—苯乙烯多嵌段共聚物的合成及性能

通过聚乙二醇、聚丙二醇、遥爪双羟基聚苯乙烯3种预聚物以甲苯二异氰酸酯（TDI）为偶联剂合成氧乙烯-氧丙烯-苯乙烯多嵌段共聚物。研究其合成条件、精制及表征,并研究其力学性能、吸水性及乳化性质。结果表明,某些组成的嵌段共聚物呈物热塑性弹性体行为,吸水率达到500%～700%。     

Synthesis,characterization and properties of amphiphilic butadiene-oxyethylene multiblock copolymers

Butadiene-oxyethylene multiblock copolymers were synthesized via coupling reaction of telechelic α,ω-dihydroxypolybutadiene (PB) and poly(ethylene glycol) with tolylene-2,4-diisocyanate. The poly(oxyethylene) (PEO) content of the purified copolymer was determined by elemental analysis and the structural parameters were calculated from number-average molecular weights of the purified copolymer, determined by membrane osmometry, and those of the prepolymers, determined by vapor pressure osmometry. The total number of blocks varied from 60 to 100. Transmission electron microscopy showed the existence of multiphases in the copolymer. Wide angle X-ray diffraction indicated that the crystallinity increased from 0 to 50% with increasing weight ratio of PEO/PB. These multiblock copolymers exhibit excellent emulsifying properties, as compared to the multiblock copolymers or graft copolymer of oxyethylene and styrene. Only 0.1 g of polymer was needed to make 100 mL of a water/toluene (9:1, w/w) mixture form an emulsion completely. When the weight ratio of water/toluene was changed from 9:1 to 7:3 or the molecular weight of PEG from 6000 to 2000, the oil-in-water type emulsion was changed to water-in-oil type. The copolymers also showed a good phase transfer catalytic effect when applied to the Williamson reaction. Conversion of potassium phenolate into butyl phenolate reached over 95% when the multiblock copolymer containing 3 mmol of PEO was used for 1 g potassium phenolate, whereas no reaction occurred without using the multiblock copolymer at 90°C for 4 h.     

吸水性热塑性橡胶——氧乙烯-氧丙烯-苯乙烯多嵌段共聚物的合成及性能

通过聚乙二醇、聚丙二醇、遥爪双羟基聚苯乙烯 3种预聚物以甲苯二异氰酸酯 (TDI)为偶联剂合成氧乙烯 -氧丙烯 -苯乙烯多嵌段共聚物。研究其合成条件、精制及表征 ,并研究其力学性能、吸水性及乳化性质。结果表明 ,某些组成的嵌段共聚物呈现热塑性弹性体行为 ,吸水率达到 5 0 0 %～70 0 %。     

Morphology and thermomechanical properties of main-chain polybenzoxazine-block-polydimethylsiloxane multiblock copolymers

The main-chain polybenzoxazine-block-polydimethylsiloxane multiblock copolymers were synthesized via the Mannich polycondensation among 4,4′-dihydroxyldiphenylisopropane, 4,4′-diaminodiphenylmethane, aminopropyl-terminated polydimethylsiloxane and paraformaldehyde. The multiblock copolymers were characterized by means of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and size exclusion chromatography (SEC). Atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS) showed that the multiblock copolymers displayed microphase-separated morphology. Owing to the presence of the main-chain polybenzoxazine blocks, the multiblock copolymers are thermally-crosslinkable. The curing behavior of the multiblock copolymers was investigated according to the analysis of non-isothermal curing kinetics. The measurement of static contact angles showed that with the inclusion of polydimethylsiloxane blocks, the polybenzoxazine thermosets resulting from the multiblock copolymers displayed the improved surface hydrophobicity.     

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.     

Effect of molecular architecture on microstructural characteristics in some polysiloxaneimide multiblock copolymers

Efforts to correlate molecular characteristics with microstructural dimensions in microphase-separated diblock and triblock copolymers have been very successful, resulting in relationships that can be utilized to design materials with a specific microstructure and, consequently, with particular thermomechanical properties. However, similar efforts in the arena of multiblock copolymers have not been nearly as extensive, despite the increasing interest and diversity of this class of materials. In the present work, energy-filtered electron microscopy (EFEM) and small-angle neutron scattering (SANS) are used in a complementary fashion to probe the phase behavior of a series of three polysiloxaneimide (PSI) multiblock copolymers with different molecular architectures. Despite their relatively short segment lengths, all three materials exhibit signs of microphase separation at ambient temperature. SANS data are obtained from chemically unaltered materials and are subsequently interpreted with the Teubner-Strey model for microemulsions. Resultant microstructural dimensions are in good agreement with those measured from EFEM micrographs. Additional insight into the intramolecular sequencing of each copolymer is obtained from scaling relationships.     

LC multiblock copolymers containing polysulfone segments. II. Material properties

The synthesis of multiblock copolymers containing liquid crystalline, semi-aromatic polyester segments of poly(ethylene terephthalate-co-oxybenzoate), and polysulfone segments with different segment molecular weights was recently described. Such block copolymers should make it possible to combine properties of the base homopolymers, e.g., the high strength of liquid crystalline polymers (LCP) with the high thermostability of polysulfone (PSU). Investigations of melt rheology and relaxation behavior discussed here demonstrated that the properties of the block copolymers are intermediate between those of the homopolymers and can be tailored by using PSU and LCP segments of suitable molecular weight. The high melt viscosity of PSU is lowered by block copolymer formation, allowing good processability by injection molding. The material properties of the resulting samples are characterized by a combination of PSU thermostability and improved strength. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 619–630, 1997     

Synthesis,characterization and rheological properties of multiblock associative copolymers by RAFT technique

Polymer Bulletin - Preparation of associating multiblock copolymer electrolytes mediated by radical addition–fragmentation chain transfer (RAFT) technique has been evaluated and reported in...     

Thermoplastic blends of physically crosslinked multiblock copolymers and copolymers with uniform grafts

Two multiblock copolymers of styrene and propylene oxide and four acrylate copolymers with uniform polystyrene grafts were prepared and blended. The blends are melt processable and their properties varied from thermoplastic elastomers to toughened plastics. The relationship between mechanical properties and composition of the thermoplastic blends indicated that all the blends exhibited a synergism, which is probably due to the increase of miscibility between the components caused by the same physical crosslinks — the glassy domains aggregated from both the polystyrene grafts and polystyrene blocks. The synergistic effect seemed more evident when two different graft copolymers were blended together than when one multiblock copolymer was blended with one graft copolymer. In all cases a maximum tensile strength appeared at the blend with 90 wt.-% of the component, possessing higher tensile strength and ultimate elongation.     

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     

Synthesis and properties of poly(ester ether) multiblock copolymers/organomontmorillonite hybrid nanocomposite

In this article, poly(ester ether) multiblock copolymer/organomontmorillonite hybrid nanocomposites were prepared via an intercalation polymerization process. The resulting hybrid nanocomposites were characterized by X‐ray diffraction, differential scanning calorimeter, and transmission electron microscopy. The results proved that the organomontmorillonite (organo‐MMT) could be exfoliated into ～ 50‐nm thickness and dispersed in the poly(ester ether) multiblock copolymer (TPEE) matrix during the intercalation polymerization process. TPEE/organo‐MMT nanocomposites showed excellent mechanical properties compared with the unfilled TPEE. When the organo‐MMT content was about 3–5 wt %, MMT could enhance the strength, modulus, and hardness of TPEE without sacrificing its elongation at break. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1716–1720, 2002; DOI 10.1002/app.10552     

烯烃多嵌段共聚物的结构、合成及应用

烯烃多嵌段共聚物是一种新型的聚烯烃热塑性弹性体,主要通过催化乙烯和1-辛烯链穿梭聚合制备得到多嵌段含"软段"和"硬段"的聚合物,其独特结构和性能已经成为新材料的研究热点.本文概述了烯烃嵌段多共聚物的结构和制备合成,并指出了烯烃多嵌段共聚物性能和应用前景.     

Synthesis and characterization of amphiphilic conetworks based on multiblock copolymers

Model amphiphilic conetworks based on cross-linked block copolymers of the hydrophilic ionizable 2-(dimethylamino)ethyl methacrylate (DMAEMA, 25 nominal units per block) and the hydrophobic n-butyl methacrylate (BuMA, 5 nominal units per block) bearing three, five, seven and nine blocks were synthesized using group transfer polymerization. 1,4-Bis(methoxytrimethylsiloxymethylene)cyclohexane and ethylene glycol dimethacrylate were used as the bifunctional initiator and the cross-linker, respectively. Network synthesis was performed by sequential monomer/cross-linker additions to the reaction flask, which was pre-loaded with tetrabutylammonium bibenzoate (polymerization catalyst), tetrahydrofuran (THF, solvent), and initiator. All linear conetwork precursors were characterized using gel permeation chromatography and proton nuclear magnetic resonance spectroscopy and found to have molecular weights (MWs) and compositions reasonably close to the theoretically expected values. All polymer conetworks were characterized in terms of their degree of swelling (DS) in THF, in neutral water, and in aqueous media as a function of the solution pH. It was found that the DSs were highest in acidic pH due to the repulsive forces and the osmotic pressure developed by the ionization of the DMAEMA units. Intermediate values of the DSs were observed in THF, whereas the lowest DSs were measured in neutral water. In THF, the DSs increased with the MWs of the (final) linear (co)polymer precursors, while in acidic water the DSs increased with the DMAEMA content in the (co)networks.     

Synthesis and properties of some hexafluoropropene-1,1-difluoroethene copolymers

Summary Hexafluoropropene (HFP) — 1,1-difluoroethene (VDF) copolymers have been synthesized in the 0–16 mole % HFP range and the results of a physico-chemical characterization by means of XRD (cristallinity index) and DSC techniques are related to the microstructure of the polymers, as determined by ¹⁹F NMR. The addition of a small percentage of the HFP comonomer does not affect the polymorphism of poly(vinyl-idenefluoride).     

Synthesis of multiblock copolymers of poly(2‐vinylpyridine) and polyoxyethylene

Telechelic dihydroxy poly(2‐vinylpyridine) (THPVP) samples with different molecular weights were synthesized by using lithium α‐methylnaphthalene as an anionic initiator in mixed solvents of benzene and tetrahydrofuran (THF). Then multiblock copolymers of poly(2‐vinylpyridine) (P2VP) and polyoxyethylene (PEO) were obtained by condensing THPVP and PEO with dichloromethane in the presence of potassium hydroxide. The effects of reaction time, molecular weight of PEO and THPVP, and raw meal ratio PEO/THPVP (w/w) were investigated. The best conditions were found. The copolymers can be purified by water and toluene. The purified copolymers were characterized by infrared (IR) and ¹H nuclear magnetic resonance (¹H‐NMR). The PEO segment content was calculated from the integral curve of ¹H‐NMR spectra. The results showed that these multiblock copolymers were connected through oxymethylene. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1632–1636, 2003     

Rheological investigation of shear-induced structure changes in multiblock copolymers

Styrene-butadiene multiblock copolymers were examined with both newly introduced and established rheological techniques and by transmission electron microscopy (TEM) to evaluate shear-induced structural changes in these polymers. Transient rheological tests (based on superposed flow principles) were developed which probed structural changes that occur in the copolymers during and at the cessation of steady shear. Data from these tests indicated that for the cylindrical morphology copolymer (SB1) there were structural changes occurring during steady shear that were recovered upon cessation of shear. The recovery process took place on time scales that could be significant in processing. The lamellar morphology material (SB2) did not exhibit this recovery behavior. Longer-term structure changes were investigated using established techniques and showed differences between the cylindrical and lamellar copolymers. When tested at 210°C, peaks in tan δ occurred at 30 rad/s for SB1 and at 0.5 rad/s for SB2 with saturation strain levels of 150 strain units (SU) for SB1 and 80 SU for SB2. TEM analysis of SB2 indicated that, although rheological changes are significant up to 80 SU, better alignment of the domain morphology can be achieved at moderately low strains of 7 SU. This indicates that the copolymers' rheological changes, which occur as a result of steady shearing, may not be due entirely to domain alignment, but may also be due to more local molecular rearrangements (e.g., chain disentanglement). © 1996 John Wiley & Sons, Inc.     

苯乙烯-环氧丙烷多嵌段共聚物的合成及表征

在端双羟基聚苯乙烯和聚丙二醇中加入偶联剂2,4-甲苯二异氰酸酯(TDI),采用一步法或二步法制备了苯乙烯-环氧丙烷多嵌段共聚物。结果表明,由二步法制备的共聚物较一步法制备共聚物中均聚物的含量少。粗产物可分别用乙醇及十氢萘萃取,以除去未反应的聚丙二醇及端双羟基聚苯乙烯。纯化物经红外光谱法、核磁共振波谱法、凝胶渗透色谱法、膜渗透压法和元素分析法测试表明,试样为聚苯乙烯与聚环氧丙烷的多嵌段共聚物。     

Synthesis and thermal analysis of styrene and α-methylstyrene multiblock copolymers

Summary Multiblock copolymers of styrene and -methylstyrene (¯M_n 70.000 g.mole^–1) with various -methylstyrene contents were synthetized by anionic polymerization. The glass transition temperatures (Tg) of these copolymers have been measured by D.T.A. A single Tg was observed over the whole composition range. This Tg obeys the derived GORDON and TAYLOR equation. Moreover these copolymers are heat resistant up to temperatures of at least 280°C.