Alder‐ene addition of maleic anhydride to polyisobutene: nuclear magnetic resonance evidence for an unconventional mechanism

In this work, the thermal Alder‐ene functionalization of highly reactive, vinylidene‐terminated, polyisobutene (PIB) with stoichiometric amounts of maleic anhydride at 200 °C was investigated by NMR spectroscopy. The thorough interpretation of the complex NMR spectra of PIB derivatives collected at different reaction times (from 4 to 21 h) was based on the combined use of one‐ and two‐dimensional techniques which allowed the precise structure of all the reaction products as well as their relative content to be ascertained. The analysis evidenced the formation of large amounts of derivatives generated by the classic Alder‐ene mechanism and involving the more reactive vinylidene ‘exo’ double bonds of PIB. More interestingly, the investigation also the investigation allowed also to detect the formation of a noteworthy amount of not expected structure generated by the thermal maleination of the less reactive PIB ‘endo’ β‐form provided by the isomerization of residual PIB ‘exo’ α‐form during the functionalization reaction. Copyright © 2012 Society of Chemical Industry     

Dynamic and static properties of SBS triblock copolymer and their blends

By using a dynamic testing method (Rheovibron), it has been established that for a pure triblock copolymer (styrene-butadiene-styrene, SBS), the morphology is composed of a continuous phase, a dispersed phase and an interphase. The predominance of the phase depends upon whether the polymer is cast from a good or poor solvent for each block. For the blends of SBS with PS and PBd, the interphase occupies a greater fraction as indicated by the fact that its corresponding molecular relaxation temperature range is much broader (10°–80°C) than that of pure SBS (60°–80°C). If the blends of SBS with its corresponding homopolymers are heated at 140°C for 45 min, the fraction of the interphase increases significantly and the onset of molecular relaxation is lowered to ?10°C. The viscosities of SBS and their blends are measured by both dynamic and static methods. Complex viscosities calculated from the dynamic method show transitions similar to those of storage moduli. Viscosities at different temperatures from these two methods are superimposed onto master curves.     

Association and physical gelation of ABA triblock copolymer in selective solvent

Association behavior and physical gelation mechanism of ABA triblock copolymer dissolved in B-selective solvent have been studied systematically from dilute to moderately concentrated solutions. Static and dynamic light scattering and nuclear magnetic resonance measurements for dilute solutions of poly(methyl methacrylate)-block-poly(tert-butyl acrylate)-block-poly(methyl methacrylate) (PMMA-PtBuA-PMMA) in 1-butanol (PtBuA selective solvent) indicated that PMMA-PtBuA-PMMA chains are molecularly dissolved above 50 °C. With decreasing temperature, the triblock copolymers form associated micelles consisting PMMA associated core and PtBuA shell. Linear dynamic viscoelastic measurements for solutions with moderate concentration (3.9-12.0 wt%) revealed that the system was viscous sol state at 60 °C. Drastic increase of shear storage modulus (G′) occurred with decreasing temperature, and at 25 °C, G′ showed rubbery plateau with weak frequency dependency, means the formation of elastic physical gel. The consistency between the temperature for micelle formation and that at the increase in G′ indicates that the physical gelation is owing to the network formation as the result of the association of PMMA chains and the bridging PtBuA chains connecting the PMMA cores. Master curves for the dynamic moduli were derived by time-temperature superposition along the frequency axis. Just above sol-gel transition concentration (C_gel), the master curves suggest the existence of fairy amount of aggregate that is not incorporated in the macroscopic network. With the increase in polymer concentration, the master curves become to reveal Maxwell-type viscoelasticity with narrow relaxation time distribution, suggesting the formation of transient network with easily generation and destruction of crosslinks. Concentration dependency of the plateau modulus is stronger than the theoretically expected, means the macroscopic transient network grows with polymer concentration by increasing the fraction of elastically effective bridging PtBuA chain above C_gel.     

Hetero-structure of ABC triblock copolymer thin film on polymer-coated substrate

The morphology and the phase diagram of the ABC block copolymer on the polymer-coated substrate were studied by using the self-consistent field theory. Due to the asymmetric surfaces for the block copolymer thin film, the rich hetero-structures occur, which are the combination of two different microstructures, such as perforated lamellar and lamellar phase (PL + L), cylindrical and lamellar phase (C + L). The phase diagrams were constructed for the identical interaction parameters case and the non-frustrated case. The effect of the film thickness is also considered at the fixed grafting density. Comparing the results, we found that the essence of the variation of the grafting density is the change of the effective film thickness in most cases. The relationship between the grafting density and the film thickness is constructed. Our results offer another way to tailor the phase behavior of the block copolymer thin film and obtain the hetero-structures on nanoscale.     

Novel zwitterionic ABA-type triblock copolymer for pH- and salt-controlled release of risperidone

An ABA-type triblock copolymer was synthesized through group-transfer polymerization by using poly[2-(diethylamino) ethyl methacrylate] (PDEA) as A block and poly[2-(dimethylamino) ethyl methacrylate] (PDMA) as B block. By utilizing the 1,3-propane sultone to obtain polyzwitterionic triblock copolymer under moderate conditions, PDMA block of the triblock copolymer has been selectively betainized. The selectively betainized block copolymer and its precursor were molecularly dissolved in acidic aqueous media without any use of cosolvent at room temperature. In both cases, an increase in solution pH caused near monodisperse cationic or neutral flower-like micellization with hydrophobic PDEA-core at basic aqueous solution. However, at higher polymer concentrations where precursor triblock copolymer does not exhibit any gelling behavior (10% and higher), polyzwitterionic copolymer derivative can be gelated as a result of inter-chain integration of polyzwitterionic groups. Furthermore, the load of risperidone (RISP) into gel matrix and release studies have been successively realized. The results indicated that the betainized novel gel is appropriate for using as a pH- and salt-controlled risperidone-releasing system.     

苯乙烯在异氰酸酯官能化二元乙丙橡胶中的作用

在苯乙烯（St）存在下,以2,5-二甲基-2,5-双（叔丁基过氧基）己烷（DHBP）为引发剂,3-异丙烯基-α,α-二甲基苄基异氰酸酯（TMI）为接枝单体,于哈克转矩密炼机中对二元乙丙橡胶（EPM）进行了自由基接枝官能化,产物用傅立叶红外光谱仪进行表征,并用化学滴定法对接枝率进行测定。实验结果表明,TMI成功地接枝到EPM上;适量St作为共单体加入体系中起到抑制EPM中PP链段的降解和提高TMI的接枝率两方面作用。     

Adhesion of styrenic triblock copolymers to miscible blends of polystyrene and a phenylene ether copolymer

The adhesion of a triblock copolymer having short styrene end-blocks and a hydrogenated mid-block to a polystyrene containing substrate was studied using both lap shear and peel test methods. The two approaches gave very similar results. Within the limits examined, the adhesive bond strength did not depend significantly on bonding temperature or time. However, the adhesive strength did increase substantially as a phenylene ether copolymer or PEC, essentially poly(phenylene oxide), was added to the substrate. This effect is believed to be the result of the exothermic mixing of PEC with polystyrene that causes an additional driving force, other than combinatorial entropy, for interpenetration of segments of the substrate and the styrenic phase of the block copolymer at the interface. Attempts to use a block copolymer having longer styrenic segments resulted in adhesive bond strengths so large that cohesive failure occurred first.     

Excimer fluorescence study on the miscibility of poly(vinyl methyl ether) and styrene-butadiene-styrene triblock copolymer

The excimer fluorescence of a triblock copolymer, styrene-butadiene-styrene (SBS) containing 48 wt% polystyrene was used to investigate its miscibility with poly(vinyl methyl ether) (PVME). The excimer-to-monomer emission intensity ratio I_M/I_E can be used as a sensitive probe to determine the miscibility level in SBS/PVME blends: I_M/I_E is a function of PVME concentration, and reaches a maximum when the blend contains 60% PVME. The cloud point curve determined by light scattering shows a pseudo upper critical solution temperature diagram, which can be attributed to the effect of PB segments in SBS. The thermally induced phase separation of SBS/PVME blends can be observed by measuring I_M/I_E, and the phase dissolution process was followed by measuring I_M/I_E at different times.     

SBS的改性进展及其在胶粘剂中的应用

概述了笨乙烯-丁二烯-苯乙烯嵌段共聚物（SBS）的结构及性能,以及在氢化、磺化、环氧化及接枝等方面的改性研究进展,并介绍了在胶粘剂中的应用。     

Synthesis of tetramethyl-p-silphenylenesiloxanedimethylsiloxane triblock copolymer by employing living anionic polymerization

Dimethylsiloxane-tetramethyl-p-silphenylenesiloxane-dimethylsiloxane (DMS-TMPS-DMS) triblock copolymer was synthesized by employing living anionic polymerization of hexamethylcyclotrisiloxane (D₃). Two synthetic methods were carried out for the polymerization. One of those methods was the anionic polymerization of D₃ initiated at the silanolate anion which was prepared from the terminal hydroxyl group of silanol-terminated TMPS prepolymer by reaction with n-butyllithium (method 1). The other was the coupling reaction of vinyl-terminated TMPS prepolymer with hydrosilyl-terminated DMS prepolymer obtained from the anionic polymerization of D₃ by using diphenylmethylsilanolate anion as initiator (method 2). In method 1, DMS contents of the copolymers ranged from 25.8 to 72.5 wt% and the values agreed with the ratio of D₃ to TMPS prepolymer. The weight-average molecular weights ranged from 1.36×10⁴ to 19.4×10⁴ and were close to the predicted values calculated from the $\text{M}\text{?}{}_{\mathrm{v}}$ of the TMPS prepolymer and the amount of D₃ added. In the case of method 2, weight-average molecular weights ranged from 19.5×10⁴ to 24.2×10⁴. The high molecular weight copolymer could thus be obtained by method 2. Intrinsic viscosity values of the triblock copolymers agreed with calculated values obtained by considering the copolymer as a binary mixture of these homopolymers. Differential scanning calorimetry and thermogravimetry were carried out on the triblock copolymers. The equilibrium melting temperatures of each of the copolymers were very close to that of poly-TMPS (160°C). The glass transition temperature and heat of fusion were decreased as the DMS content was increased. The thermogravimetric curves for the copolymers indicated that the thermal stability of the triblock copolymer was intermediate between the DMS and TMPS homopolymers.     

Synthesis and evaluation of new amphiphilic polyethylene glycol-based triblock copolymer surfactants

We report in this investigation the synthesis of a new series of amphiphilic ABA-triblock copolymers consisting of double-chain hydrophobic moieties (A) of different chain lengths attached to each end of polyethylene glycols of different molecular weights (B). The identities of the prepared compounds were confirmed by elemental and Fourier transform infrared analyses. The prepared compounds showed good water solubility. Some of their surface properties, such as the critical micelle concentration, effectiveness of water surface tension reduction, surface excess concentration, standard free energies of adsorption and micellization, and surface area per molecule, were determined.     

苯乙烯-乙烯/丁烯-苯乙烯三嵌段共聚物用填充油的制备及性能

采用增塑剂N 4006与不同黏度的石蜡基基础油进行调配,并加入不同种类及用量的光、热稳定剂,制备了2种苯乙烯-乙烯/丁烯-苯乙烯三嵌段共聚物(SEBS)用填充油(填充油A和填充油B),并对其光安定性及热安定性进行了研究。结果表明,紫外吸收剂G-1与酚胺类复合热稳定剂R-2有显著协同作用,可有效改善油品的光、热安定性。SEBS填充油B在加入光稳定剂G-1和热稳定剂R-2后,可达到较高的光、热安定性,光热稳定剂的最佳质量分数均为0.03%。     

Self-assembly of a liquid crystal ABA triblock copolymer in a nematic liquid crystal solvent

An ABA type triblock copolymer, consisting of liquid crystalline polymer (LCP, poly(4-cyanobiphenyl-4-oxyundecylacrylate)) ‘A’ end blocks and a deuterated polystyrene (dPS) ‘B’ mid block (LCP–dPS–LCP) was successfully synthesized by atom transfer radical polymerization (ATRP). The number average molecular weight (M_n) of LCP–dPS–LCP was LCP (7.1 K)–dPS (19.4 K)–LCP (7.1 K) with a polydispersity index (PDI) of 1.41. LCP–dPS–LCP was self-assembled in a nematic liquid crystal solvent of 4-pentyl-4′-cyanobiphenyl (5CB) into spherical micelles with a LCP corona and a dPS core, in which dPS was folded to produce a V-shape structure. Micellar structures of LCP–dPS–LCP in 5CB were examined by small angle neutron scattering at various block copolymer concentrations and temperatures using a curve fitting method. The critical micelle concentration was 0.25 wt% and the self-assembled micelles dissociated into unimers at 33 °C, which is lower than the nematic to isotropic transition temperature (T_ni) of 5CB (36 °C). The entropic penalty imposed on dPS by the ordered nematic state of the 5CB solvent caused phase separation of the flexible dPS block to form micelles, which vanished above the T_ni of the 5CB solvent. Magnetic field-induced global orientation of 5CB revealed the structure of the dPS core of the micelle to be prolate (an elongated sphere) oriented with its long axis along the direction of the applied magnetic field.     

Synthesis and micellar characterization of novel pH-sensitive thiol-ended triblock copolymer via combination of RAFT and ROP processes

A new pH- sensitive thiol-ended amphiphilic triblock copolymer was synthesized by reversible addition fragmentation chain transfer polymerization. The critical micelle concentration (CMC) value for the synthesized PAA-b-PDMAEMAQ-b-PCL-SH triblock copolymer was determined to be 0.0079?g?L-1 using fluorescence probe technique. The average sizes of PAA-b-PDMAEMAQ-b-PCL-SH micelles was obtained to be 30?±?5?nm using TEM observation. It is expected that the synthesized PAA-b-PDMAEMAQ-b-PCL-SH triblock copolymer considered as a prospective candidate in nanomedicine applications such as chemo-photothermal therapy and drug delivery, mainly due to the strong affinity of thiol-ended group toward gold nanoparticle and its excellent micellization behavior.     

聚乙二醇/聚己内酯三嵌段共聚物的合成与表征

以甲苯二异氰酸酯 (TDI)为偶联剂 ,合成了聚乙二醇 (PEG) /聚己内酯 (PCL)两亲性三嵌段共聚物 (PEG-b-PCL -b -PEG ,PECL) ,采用IR、1 H-NMR、DSC和WAXD分析和研究了PECL的结构与性能。实验结果表明 ,PECL的结构和组成与设计相一致 ,结晶度和熔点均低于均聚物 ,且随着PECL中PCL嵌段含量的增加 ,PCL嵌段熔点升高。透射电镜照片显示PECL纳米粒呈核 /壳结构的球形。     

苯乙烯-丁二烯-苯乙烯嵌段共聚物的环氧化研究

采用甲酸和过氧化氢（H2O2）原位生成的过氧甲酸对苯乙烯-丁二烯-苯乙烯（SBS）进行环氧化改性，制备了环氧化SBS（ESBS）。研究了原料摩尔配比及工艺条件对其环氧基质量分数的影响，利用GPC、FT—IR、^1H—NMR等手段对ESBS的结构进行了表征。结果表明，丁二烯链段上双键的反应活性大小次序为：顺-1，4-结构〉反-1，4-结构〉1，2-结构。在SBS的环氧化反应过程中，会伴有少量环氧基发生开环副反应。当SBS中C—C双键、甲酸和H202的物质的量配比为1／0．5／0．6，反应时间为2h，反应温度为60℃时，ESBS的环氧基质量分数最高，达到了18．1％。在体系中加入少量的聚乙二醇，有利于ESBS环氧慕盾量务教的提高．     

Alder烯反应及其在天然产物合成中的应用

简要介绍了Alder烯反应及其在有机合成中的应用.着重介绍了烯反应在天然产物合成中的应用。     

Alder Ene functionalization of polypropylene through reactive extrusion

A commercial isotactic polypropylene was degraded to increase its terminal vinylidene group concentration, and it was subsequently functionalized with maleic anhydride through the Alder Ene reaction at temperatures above 200°C in a co‐rotating twin screw extruder. Characterization of the maleated product by Fourier transform infrared spectroscopy, ¹H NMR, differential scanning calorimetry, and gel permeation chromatography showed the anhydride group to be terminally attached, and the degree of functionalization was determined by infrared analysis. Increased temperature and maleic anhydride concentration, as well as improved mixing in the extruder, were found to improve the extent of the reaction. The catalytic contribution of Lewis acid species was evaluated, and ruthenium chloride was found to increase the extent of the reaction by 16% in comparison with stannous chloride as a catalyst in the Alder Ene reaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 503–516, 1999     

Miscibility study of polycarbonate and SBS triblock copolymer blends

Polymer blends of Polycarbonate (PC) and Styrene-Butadiene-Styrene triblock (SBS) have been investigated. SBS copolymers have four different styrenic contents, three of which are linear SBS. PC and PS blends are partially miscible as revealed by dynamic mechanical analysis with two clear Tgs near 100–150°C. On the contrary, PC/SBS blends have only one Tg with a left shoulder. Based on the PS domain model of pure SBS, we suggest a micelle model based on the structure when the micelle and absorb PC in the PC/SBS blends. The micelle plays an important role in improving the miscibility. The proposed micelle model has been empolyed to interpret the testing results, such as toughness, impact strength, dynamic mechanical property and SEM morphologies. This proposed micelle model seems a worth-while method to explain the properties of partialtly miscible blends of PC and SBS.     

二嵌段SB对SBS性能的影响

用GPC测定了苯乙烯类热塑性弹性体（SBS）合成过程中生成的二嵌段SB质量分数，讨论了其对SBS力学性能和加工性能的影响。结果表明，SB质量分数分别为21％和12％时，相应的线型和星形SBS的拉伸强度和300％定伸应力下降较大。随着SB质量分数的增加，线型SBS的扯断伸长率和永久变形增加，而星形SBS的变化不明显。适量的SB有利于加工，原因是二嵌段SB和SB进行相分离时，SB的两段进入SBS相应的微区，质量分数较小时不破坏网络结构，但却增大高温流动性。