Comparison of Polarity Indices and HLB Coefficients of Block Copolymers of Ethylene and Butylene Oxides of Type EBE with Nonionics Containing One Polyoxyethylene Chain

The concept of the effective chain length and the hydrophobicity index was modified and adopted for block copolymers of ethylene and butylene oxides. The effective contents of the polyoxyethylene chain and hydrophilicity indices were determined, and an improved equation for the calculation of HLB values of ethylene and butylene oxide block copolymers is proposed. The method for the estimation of the polarity index is also given.     

聚偏氟乙烯-b-聚乙烯基吡咯烷酮嵌段共聚物的制备和结构

以C₆F₁₃I为链转移剂,通过碘转移乳液聚合制得碘封端的聚偏氟乙烯（PVDF-I）,再以PVDF-I为大分子链转移剂进行N-乙烯基吡咯烷酮碘转移溶液聚合,得到聚偏氟乙烯-b-聚乙烯基吡咯烷酮（PVDF-b-PVP）两亲性嵌段共聚物;采用NMR、IR、XRD、DSC和AFM等对PVDF-b-PVP嵌段共聚物的分子和相态结构进行了表征。发现PVP能有效嵌入PVDF与末端碘之间,PVDF嵌段PVP后,PVDF分子链的有序度明显降低,产生γ晶型PVDF,同时结晶温度和结晶度降低。PVDF-b-PVP嵌段共聚物表现微相分离结构,相分离尺寸约20 nm,其亲水性也优于PVDF均聚物。     

可逆加成-断裂链转移聚合制备聚氯乙烯-b-聚乙二醇-b-聚氯乙烯共聚物

合成了含黄原酸酯端基的聚乙二醇（X-PEG-X）大分子链转移剂,并以其为可逆加成-断裂链转移试剂调控氯乙烯（VC）溶液和悬浮聚合,合成聚氯乙烯-b-聚乙二醇-b-聚氯乙烯（PVC-b-PEG-b-PVC）三嵌段共聚物。X-PEG-X调控VC溶液聚合得到的共聚物的分子量随聚合时间增加而增大,分子量分布指数小于1.65。X-PEG-X具有水/油两相分配和可显著降低水/油界面张力的特性,以X-PEG-X为链转移剂和分散剂,通过自稳定悬浮聚合也可合成PVC-b-PEG-b-PVC共聚物,共聚物颗粒无皮膜结构,分子量随聚合时间增加而增大;由于VC悬浮聚合具有聚合物富相和单体富相两相聚合特性,共聚物分子量分布指数略大于溶液聚合共聚物。通过乙酸乙烯酯（VAc）扩链反应进一步证实了PVC-b-PEG-b-PVC的“活性”,并合成PVAc-b-PVC-b-PEG-b-PVC-b-PVAc共聚物。水接触角测试表明PVC-b-PEG-b-PVC的亲水性优于PVC。     

电子束辐照接枝改性聚乳酸及其降解性能的研究

为改善聚乳酸（Polylactic acid,PLA）材料的亲水性,采用电子束辐照接枝亲水性单体N-乙烯基吡咯烷酮（N-vinyl pyrrolidone,NVP）对其进行表面改性。研究了吸收剂量和反应介质中酸浓度对PLA接枝率和分子量影响,并对PLA-g-PVP的降解性能进行了考察。结果表明,接枝率随着辐照剂量的增加而提高;当反应介质中酸浓度为0.07mol/L时PLA的分子量达到极大值;接枝共聚物（PLA-g-PVP）的吸水率和降解速度较PLA明显提高。接枝率为12.1%的PLA-g-PVP共聚物降解48h后吸水率为11.5%,是PLA的16.4倍;接枝率为8.8%的共聚物168h分子量损失率为82.6%,是PLA的2.4倍。     

Characterization and water vapor sorption property of ABA‐type triblock copolymers derived from polyimide and poly(methyl methacrylate)

The characterization of ABA‐type triblock copolymer films derived from polyimide (PI) macroinitiator and poly(methyl methacrylate) (PMMA) synthesized by atom transfer radical polymerization was investigated by focusing on different block lengths of PMMA. The hydrophobic property tends to increase with increasing PMMA content in the triblock copolymers, while the PMMA blocks enhance the charge transfer interaction between the PI segments. The water vapor sorption measurement of triblock copolymers was determined at 35 °C. The water vapor solubility of triblock copolymers tends to decrease with increasing PMMA content. In addition, linear correlations were observed between the solubility and polymer‐free volume and polymer molecular polarity in triblock copolymers as well as in other conventional polymer families. According to Zimm?Lundberg analysis, the PMMA block segments in the triblock copolymers accelerate water vapor clustering due to the high mobility of PMMA. The mobility of PMMA block segments strongly affected not only physical properties but also the water vapor solubility of the triblock copolymers. The ABA triblock copolymerization composed of PI and PMMA is one of the effective ways to improve the hydrophobic property. © 2013 Society of Chemical Industry     

Protein encapsulation in biodegradable amphiphilic microspheres. I. Polymer synthesis and characterization and microsphere elaboration

Polymerization of lactide on monomethoxypolyoxyethylene (MPOE), using stannous octoate as a catalyst, was carried out in bulk and in solvent. Polymerization in a solvent permits one to work at a lower temperature and thus to prevent transesterification reactions. The copolymers synthesized in solvent exhibited a lower polydispersity and a polylactic acid (PLA) block longer and closer to the expected one. Therefore, this procedure was used to synthesize a series of diblock copolymers MPOE–D ,L -PLA, keeping the PLA chain constant (45,000 g/mol), the MPOE block increasing from 2000 to 5000, 10,000, 15,000, and 20,000 g/mol. The longer the MPOE chain, the higher the water uptake in the MPOE–PLA films and the lower the glass transition temperature of the copolymers. The synthesized copolymers were used to prepare microspheres by the double-emulsion method. The PLA microspheres possess a smooth surface, whereas those made from copolymers have a rough surface with irregularity increasing with the molecular weight of MPOE. The size of these microspheres depends on the amphiphilic nature of the copolymers, their hydrophilicity, and their intrinsic viscosity in the organic solvent. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1695–1702, 1998     

Surface characterization of biocompatible polysulfone membranes modified with poly(ethylene glycol) derivatives

Self-transformable and blood compatible devices of sulfonated poly(ethylene glycol) acrylate diblock copolymer (PEG-SO₃A/OA) with hydrophilic and hydrophobic block entrapped to polysulfone membrane surface were investigated in terms of the degree of hydrophilicity. The asymmetric membrane was formed by phase inversion process, and the induced hydrophilicity by reorientation of diblock copolymer at interface was verified with contact angle measurement, electron spectroscopy for chemical analysis (ESCA) depth profiling with ion sputtering and platelet adhesion test. Molecular dynamics (MD) simulations for the interface of hydration layer were also performed with various hydrophilic copolymer densities to gain optimum interfacial structure in information. The dependency of water clustering behavior around diblock copolymers as a hydrophilicity parameter was described in terms of atom-atom radial distribution function (RDF). The results showed that the diblock copolymer entrapped surfaces demonstrated less platelet adhesion than control or copolymers having no hydrophobic blocks. In addition, oxygen composition significantly began to decrease deeper into the membrane, indicating the reorientation of diblock chains. Copolymer entrapped surfaces significantly induced the degree of water clustering, and the resulting equilibrium rearrangement of interfacial structures was distinctly dependent upon the density of copolymer. Taken together, the results show that the novel concept ofin situ self-transformable surface modification strategy was successfully developed for biocompatible ultrathin biomedical membrane device.     

生物相容性聚酯共聚物PBS-b-PEG的合成与性能

以1,4-丁二酸、1,4-丁二醇和聚乙二醇(PEG)为主要原料进行熔融缩聚,制备了不同PEG含量的PEG-聚丁二酸丁二酯(PBS)嵌段共聚物(PBS-b-PEG).核磁共振和凝胶渗透色谱分析表明:合成的PBS-b-PEG结构明确.透过差示扫描量热仪、广角X射线衍射仪、偏光显微镜、原子力显微镜和接触角分析仪研究了共聚物的...     

RAFT polymerization of temperature- and salt-responsive block copolymers as reversible hydrogels

Reversible-addition fragmentation chain transfer (RAFT) polymerization enabled the synthesis of novel, stimuli-responsive, AB and ABA block copolymers. The B block contained oligo(ethylene glycol) methyl ether methacrylate (OEG) and was permanently hydrophilic in the conditions examined. The A block consisted of diethylene glycol methyl ether methacrylate (DEG) and [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TMA). The A block displayed both salt- and temperature-response with lower critical solution temperatures (LCSTs) dependent on the molar content of TMA and the presence of salt. Higher TMA content in the AB diblock copolymers increased the critical micelle temperatures (CMT) in HPLC-grade water due to an increased hydrophilicity of the A block. Upon addition of 0.9 wt% NaCl, the CMTs of poly(OEG-b-DEG₉₅TMA₅) decreased from 50 °C to 36 °C due to screening of electrostatic repulsion between the TMA units. ABA triblock copolymers displayed excellent hydrogel properties with salt- and temperature-dependent gel points. TMA incorporation in the A block increased the gel points for all triblock copolymers, and salt-response increased with higher TMA composition in the A block. For example, poly(DEG₉₈TMA₂-b-OEG-b-DEG₉₈TMA₂) formed a hydrogel at 40 °C in HPLC-grade water and 26 °C in 0.9 wt% NaCl aqueous solution. These salt- and temperature-responsive AB diblock and ABA triblock copolymers find applications as drug delivery vehicles, adhesives, and hydrogels.     

Synthesis of PEGylated poly(amino acid) pentablock copolymers and their self‐assembly

Pentablock copolymers with an ABCBA architecture were synthesized by ring‐opening polymerization of N‐carboxyanhydrides of l ‐leucine and γ‐benzyl l ‐glutamate using an α, ω‐diamino poly(ethylene glycol) (PEG) as macroinitiator. Three different PEGs with molecular weights of 2000, 4600 and 10 000 Da were used and the poly(amino acid) (PAA) block lengths were set to a combined 10 and 40, respectively, repeat units for p(l ‐Leu) and 40 repeat units for p(l ‐Glu). The molecular architecture of the resulting pentablock copolymers was determined by the order of monomer addition. The living character of the N‐carboxyanhydride ring‐opening polymerization enables the formation of multiblock copolymers. The degree of polymerization for the PAA blocks matched the monomer/initiator ratio. A structural switch element, which controls the hydrophilicity of the pentablock copolymers, was incorporated in the form of the p(l ‐Glu) blocks. The pentablock copolymers became water soluble after hydrolyzing the benzyl ester protective groups. The pentablock copolymers self‐assembled into polymeric aggregates ranging in size between 160 and 340 nm. Hydrogels formed readily if the central PEG block had a molecular weight of at least 4600 Da and the terminal A‐blocks consisted of p(l ‐Leu). SEM images confirmed the size ranges of the polymeric aggregates and showed non‐distinct spherical aggregates. © 2016 Society of Chemical Industry     

Synthesis and properties of novel biodegradable triblock copolymers of poly(5-methyl-5-methoxycarbonyl-1,3-dioxan-2-one) and poly(ethylene glycol)

Novel biodegradable triblock copolymers of poly(5-methyl-5-methoxycarbonyl-1,3-dioxan-2-one) (PMMTC) with poly(ethylene glycol) (PEG), PMMTC-b-PEG-b-PMMTC, were synthesized by the ring-opening polymerization of MMTC in bulk, using the dihydroxyl PEG as initiator and Sn(Oct)₂ as catalyst. The triblock copolymers with different compositions were characterized by IR and ¹H NMR, their molecular weight was measured by gel permeation chromatography (GPC). The results showed that the molecular weight of triblock copolymers increased either with the increase of the molar ratio of MMTC in feed while the PEG chain length kept constant, or by lengthening the backbone chain of PEG block with the same ratio of MMTC in feed. The hydrophilicity of copolymers was greatly improved by incorporation of PEG block into polycarbonate. The in vitro hydrolytic/enzymatic degradation and controlled drug release properties of the triblock copolymers were also investigated.     

Synthesis of PDON-b-PEG-b-PDON block copolymers and drug delivery system thereof

ABA-type block copolymers of poly(1,4-dioxan-2-one) (PDON) with poly(ethylene glycol) (PEG) were synthesized and characterized. From the results of differential scanning calorimetry and wide-angle X-ray diffraction, it was observed that the PDON blocks show similar crystallization behavior with homopolymer while the PEG blocks demonstrate lower melting temperature and crystallinity than PEG homopolymer. Their dynamic contact angles (θ_a) decreased with the increase of PEG fraction in copolymers, indicating the hydrophilicity of PDON-b-PEG-b-PDON (PDPEPD) copolymers was improved gradually. The potential application of PDPEPD copolymers in the drug delivery system has been investigated. The release rate of Levonorgestrel (LNG) increased with the strengthening of hydrophilicity of copolymer samples. The burst effect of release of LNG is small in copolymers with short PDON blocks. When DON mole fraction in copolymers is high enough, no burst effect can be observed. In an experimental period of about 25 days, the release rate of LNG kept almost constant. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 2121–2128, 1998     

Formation of ordered microporous films with water as templates from poly(D,L‐lactic‐co‐glycolic acid) solution

Recently a method that uses water droplets at the air–solution interface as an ordered template was reported for the preparation of ordered micrometer‐size honeycomb structures. Here we show that the method can also be used for formation of honeycomb‐like porous films from random copolymers with certain hydrophilicity, besides those polymers with defined structures such as block copolymers, starlike homopolymers, amd amphiphilic polymers. This demonstrates that the stabilization of water droplets is the key factor for the regular structure. Also we indicate that size and structure of the films can be regulated by such variables as concentration and atmospheric humidity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1846–1850, 2003     

Synthesis, characterization and aggregation behavior of block copolymers containing a polyisocyanopeptide segment

Following up on previous preliminary communications the synthesis of a series of block copolymers by applying amine end-capped polymers as initiators for the nickel(II) catalyzed polymerization of isocyanides is reported. Using a polystyrene derivative as the initiator, superamphiphiles containing a hydrophobic polystyrene tail and a charged helical polyisocyanide headgroup were prepared. Under proper conditions these superamphiphiles self-assembled in water to give a variety of aggregate morphologies, among which are superhelical architectures. Initiators derived from carbosilane dendritic wedges gave block copolymers with a unique combination of structural elements, i.e. a flexible dendritic block and a rigid polyisocyanide block. Block copolymers derived from the 3rd generation dendrimers form well-defined micellar aggregates in the presence of Ag⁺ ions. These aggregates have been used to construct nanoarrays of metallic silver.     

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     

Synthesis and characterization of poly(L‐lactide)‐poly(ethylene glycol) multiblock copolymers

Poly(L‐lactide)‐poly(ethylene glycol) multiblock copolymers with predetermined block lengths were synthesized by polycondensation of PLA diols and PEG diacids. The reaction was carried out under mild conditions, using dicyclohexylcarbodiimide as the coupling agent and dimethylaminopyridine as the catalyst. The resulting copolymers were characterized by various analytical techniques, such as GPC, viscometry, ¹H‐NMR, FTIR, DSC, X‐ray diffractometry, and contact angle measurement. The results indicated that these copolymers presented outstanding properties pertinent to biomedical use, including better miscibility between the two components, low crystallinity, and hydrophilicity. Moreover, the properties of the copolymers can be modulated by adjusting the block length of the two components or the reaction conditions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1729–1736, 2002; DOI 10.1002/app.10580     

电子束辐照接枝改性聚乳酸及其降解性能

为改善聚乳酸(polylactic acid,PLA)材料的亲水性,采用电子束辐照接枝亲水性单体N-乙烯基吡咯烷酮对其表面进行改性,得到接枝共聚物PLA-g-PVP。研究了吸收剂用量和反应介质中酸的浓度对PLA接枝率和PLA-g-PVP黏均相对分子质量(简称分子量,下同)的影响,并对PLA-g-PVP的降解性能进行了考察。结果表明,PLA接枝率随着辐照剂量的增加而提高;当反应介质中酸的浓度为0.07 mol/L时PLA-g-PVP的分子量达到极大值;PLA-g-PVP的吸水率和降解速度较PLA明显提高。接枝率为12.1%的PLA-g-PVP共聚物降解48 h后,吸水率为11.5%,是PLA的16.4倍;接枝率为8.8%的PLA-g-PVP共聚物降解168 h后,分子量损失率为82.6%,是PLA的2.4倍。     

Synthesis and characterization of phenylquinoxaline-arylene ester block copolymers

Summary Phenylquinoxaline-arylene ester block copolymers were prepared from phenolic hydroxyl terminated oligomers of defined molecular weight using an oligomer/monomer(s) approach, in which generation of the ester linkage coupling the blocks occurred concomitantly with the growth of the polyester block. The molecular weight of the phenylquinoxaline block was held constant at 12,900, while the stoichiometry of the arylene ester monomers were adjusted to afford copolymers containing 15, 30, and 50 wt% poly(arylene ester). These copolymers represent the first example of PPQ-based block copolymers derived from well defined phenylquinoxaline oligomers.     

pH- and temperature-responsive amphiphilic diblock copolymers of 4-vinylpyridine and oligoethyleneglycol methacrylate synthesized by RAFT polymerization

Diblock copolymers of 4-vinylpyridine (4VP) and oligoethyleneglycol methyl ether methacrylate (OEGMA) were synthesized for the first time using RAFT polymerization technique as potential drug delivery systems. Effects of the number of ethylene glycol units in OEGMA, chain length of hydrophobic P4VP block, pH, concentration and temperature on the solution behavior of the copolymers were investigated comprehensively. Copolymer chains formed micelles at pH values higher than 5 whereas unimeric polymers were observed to exist below pH 5, owing to the repulsion between positively charged P4VP blocks. The size of the micelles was dependent on the relative length of blocks, P4VP and POEGMA. Thermo-responsive properties of copolymers were investigated depending on the pH and length of P4VP block. The increase in the length of P4VP block decreased the LCST substantially at pH 7. At pH 3, LCST of copolymers shifted to higher temperatures due to the increased interaction of copolymers with water through positively charged P4VP block.     

两亲扩展型共聚物的合成及中间极性嵌段对乳化性能的影响

采用聚乙二醇单甲醚(Mn=1 900,5 000)分别引发丙交酯和ε-己内酯开环聚合合成了中间嵌段(PLA)聚合度递增的聚乙二醇-聚丙交酯-聚己内酯(MPEG-PLA-PCL)两亲扩展型共聚物和相应的聚乙二醇-聚己内酯(MPEG-PCL)两嵌段共聚物。用FTIR、1HNMR和GPC对产物结构进行了表征,研究了共聚物和常规低分子表面活性剂的乳化性能,探讨了中间极性嵌段的长度对共聚物乳化性能的影响。结果表明,对于甲苯/水体系,共聚物可用于制备稳定的O/W型乳液,且三嵌段共聚物的乳化性能优于低分子表面活性剂;随着引入PLA嵌段聚合度的增加,共聚物的乳化能力呈先增加后减小的趋势;相对于MPEG1900系列共聚物,MPEG5000系列共聚物中需要引入更长的中间嵌段才能获得最佳乳化性能。