New block copolymers. 1. Synthesis and characterization of an (a–b)n type block copolymer

A new (A–B)_n type block copolymer has been synthesized by polycondensation of acidchloride terminated poly(ethylene-terephthalate) with amine-terminated butadiene acrylonitrile rubber (ATBN). The acid chloride terminated poly(ethylene-terephthalate) was synthesized by reacting terephthaloyl chloride with ethylene glycol using N,N-dimethyl formamide as the solvent. The resulting polymer was characterized by nitrogen analysis, IR and NMR spectroscopy. The solubility characteristics, solution viscosity behaviour, crystallinity, and phase characteristics of the polymer have been studied.     

Synthesis and characterization of well-defined hydrophilic block copolymer brushes by aqueous ATRP

Homopolymer brushes of poly(N,N-dimethylacrylamide) (PDMA), poly(methoxyethylacrylamide) (PMEA) and poly(N-isopropylacrylamide)(PNIPAM) grown on atom transfer radical polymerization (ATRP) initiator functionalized latex particles were used as macroinitiators for the synthesis of PDMA-b-PNIPAM/PMEA, PMEA-b-PDMA/PNIPAM and PNIPAM-b-PDMA block copolymer brushes by surface initiated aqueous ATRP. The grafted homopolymer and block copolymer brushes were analyzed for molecular weight, molecular weight distribution, chain grafting density, composition and hydrodynamic thickness (HT) using gel permeation chromatography-multi-angle laser light scattering, ¹H NMR, particle size analysis and atomic force microscopy (AFM) techniques. The measured graft molecular weight increased following the second ATRP reaction in all cases, indicating the second block had been added. Chain growth depended on the nature of the monomer used for block copolymerization and its concentration. Unimodal distribution of polymer chains in GPC with non-overlap of molar mass-elution volume curves implied an efficient block copolymerization. This was supported by the increase in HT measured by particle size analysis, equilibrium thickness observed by AFM and the composition of the block copolymer layer by ¹H NMR analysis, both in situ and on cleaved chains in solution. ¹H NMR analysis of the grafted latex and cleaved polymers from the surface demonstrated that accurate determination of the copolymer composition by this method is possible without detaching polymer chains from surface. Block copolymer brushes obey the same power law dependence of HT on molecular weight as homopolymer brushes in good solvent conditions. The NIPAM-containing block copolymer brushes were sensitive to changes in the environment as shown by a decrease in HT with increase in the temperature of the medium.     

New self-assembling biocompatible-biodegradable amphiphilic block copolymers

New biodegradable-biocompatible amphiphilic block copolymers were prepared in good yields by SnOct₂ catalyzed ring opening polymerization of ε-caprolactone initiated by monomethoxy-terminated poly(ethylene glycol) (MPEG). Coupling of the AB copolymers with hexamethylene diisocyanate afforded ABA (formally ABBA) block copolymers. Both AB and ABA copolymers were thoroughly characterized by IR and NMR spectroscopy, size exclusion chromatography, TGA and DSC thermal analysis. In particular, DSC measurements evidenced that the copolymer hydrophilic-lipophilic balance appreciably affected the state of adsorbed water. Polarized optical microscopy of bulk materials and pyrene fluorescence emission of polymer water solutions highlighted the copolymer tendency to phase separation and self-organization, respectively. Most of the prepared materials formed micelles in water and the copolymer structure appreciably affected their critical micellar concentration. In vitro cytocompatibility tests confirmed the low toxicity of the prepared polymeric materials which enhances their potential for biomedical applications.     

四官能度过氧化物JWEB50引发的PS-b-PMMA合成与表征

引言嵌段共聚物是具有两种或两种以上不同链段的聚合物,不同链段间存在的化学键限制了聚合物的相分离程度,易形成微相分离结构[1],而嵌段共聚物能作为聚合物共混体系的相容剂,只需加入少量     

Photo-responsive block copolymer containing azobenzene group: Synthesis by reversible addition-fragmentation chain transfer polymerization and characterization

The design and synthesis of a new azobenzene-based methacrylate monomer (Azo-IEM) was demonstrated, and its polymerization behavior during reversible addition-fragmentation chain transfer (RAFT) polymerization was investigated. Well-defined homopolymer and amphiphilic block copolymer containing Azo-IEM monomeric units were successfully prepared as evidenced by NMR and GPC analysis. Moreover, the photo-triggered reversible isomerization of polymer products in selected solvents was investigated. Finally, TEM analysis showed that there were significant differences in the nanoparticle morphologies when the block copolymer samples were irradiated with different wavelengths of light (i.e., UV and visible). The size and shapes of the p(HEMA-b-Azo-IEM) polymer capable of transitions upon changes in Vis/UV light exposure which prepared from MeOH/CHCl₃ mixture solvent. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47870.     

Chiorosulfonated block copolymers

Rubber-phase chlorosulforiated polystyrene-poly-(ethylene-butene-1)-polystyrene block copolymers were prepared by reaction of the block copolymer in solution with SO₂ and C1₂. Sample compositions ranged up to 7 weight percent sulfur and 29 weight percent chlorine contents as determined by X-ray fluorescence and infrared spectroscopy. A series of chlorosulfonated derivatives of an analogue of the elastomeric midblock were prepared and analyzed in similar fashion. A comparison of dynamic mechanical and dielectric behavior of solvent cast films of the block copolymer and midblock polymer materials indicates the existence of sulfonyl chloride dipole-dipole complexes in the solid state. Further evidence for the presence of such aggregates was obtained from analysis by Fourier-transform infrared spectroscopy. It appears that polystyrene domains in the block copolymer materials hinder this aggregation up to moderate concentrations of the sulfonyl chloride group as compared with the relatively unrestrained aggregate formation in the analogue midblock materials. At high levels of substitution, the formation of dipole aggregates disrupts the integrity of the polystyrene domain structure in the block copolymer materials, resulting in a reduction in mechanical strength.     

Mechanical relaxations of nylon–polyurea block copolymers

Dynamic mechanical analysis from ?150 to +150°C has been carried out on seven block copolymers that were prepared by the in situ anionic polymerization of caprolactam in the presence of a preformed polyurea. The various relaxations have been identified and activation energies calculated. Some polymer–polymer miscibility of the polyurea and amorphous nylon copolymer segments is indicated by the compositional dependence of the α relaxation.     

All-conjugated block copolymers

All-conjugated block copolymers of the rod-rod type came into the focus of interest because of their unique and attractive combination of nanostructure formation and electronic activity. Potential applications in a next generation of organic polymer materials for photovoltaic devices ("bulk heterojunction"-type solar cells) or (bio)sensors have been proposed. Combining the fascinating self-assembly properties of block copolymers with the active electronic and/or optical function of conjugated polymers in all-conjugated block copolymers is, therefore, a very challenging goal of synthetic polymer chemistry. First examples of such all-conjugated block copolymers from a couple of research groups all over the world demonstrate possible synthetic approaches and the rich application potential in electronic devices. A crucial point in such a development of novel polymer materials is a rational control over their nanostructure formation. All-conjugated di- or triblock copolymers may allow for an organization of the copolymer materials into large-area ordered arrays with a length scale of nanostructure formation of the order of the exciton diffusion length of organic semiconductors (typically ca. 10 nm). Especially for amphiphilic, all-conjugated copolymers the formation of well-defined supramolecular structures (vesicles) has been observed. However, intense further research is necessary toward tailor-made, all-conjugated block copolymers for specific applications. The search for optimized block copolymer materials should consider the electronic as well as the morphological (self-assembly) properties.     

Synthesis and characterization of energetic GAP‐b‐PAEMA block copolymer

Energetic block copolymer of polyglycidylazide‐b‐poly (azidoethyl methacrylate) (GAP‐b‐PAEMA) was synthesized and characterized. Macroinitiator PECH‐Br prepared via the reaction of 2‐bromoisobutyryl bromide with hydroxyl‐terminated polyepichlorohydrin (PECH‐OH) was used to initiate the atom transfer radical polymerization (ATRP) of chloroethyl methacrylate (CEMA). After azidation of the resulting copolymer, energetic copolymer GAP‐b‐PAEMA was obtained. Increase in the molecular weight determined by gel permeation chromatograph (GPC) is in agreement with the formation of block copolymer. Fourier transform infrared spectroscopy (FTIR) shows that the chlorine groups in the block copolymer can be substituted by azide group easily. Thermogravimetric analysis (TGA) shows that degradation of GAP‐b‐PAEMA involves two steps: the instantaneous decomposition of the azide groups followed by progressive scission of the polymer backbone. From differential scanning calorimetry (DSC) analysis, the GAP‐b‐PAEMA copolymer exhibits two glass transition temperatures (T_g) at ?18 and 36°C, suggesting that the synthesized copolymer is a thermoplastic elastomer. This research provides a new method for the synthesis of energetic polymer. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Structural effect of a series of block copolymers consisting of poly(N-isopropylacrylamide) and poly(N-hydroxyethylacrylamide) on thermoresponsive behavior

Well-defined diblock and triblock copolymers consisting of poly(N-isopropylacrylamide) (PNIPAM) and poly(N-hydroxyethylacrylamide) (PHEAA) were prepared using the atom transfer radical polymerization (ATRP) method. The number-average molecular weight and fraction of each segment were precisely controllable by adjusting the monomer/initiator ratio in feed. The lower critical solution temperature (LCST) of a series of block copolymers with different compositions was examined using a turbidimetry analysis. The copolymers with a relatively lower molar fraction of HEAA units in the polymer chain exhibited phase transition phenomenon, in which the LCST depended on the fraction in the copolymer. On the other hand, the LCST disappeared for the copolymers with higher HEAA unit molar fractions. The ¹H NMR measurement clarified that the disappearance of the LCST was attributed to the formation of the water-soluble micelle. Furthermore, the thermoresponsive property of the series of block copolymers was elucidated on the basis of the structural effect of the copolymer, which includes the order and length of the block segments.     

Thermal oxidation of polyethylene terephthalate — acrylic acid copolymers and ionomers

A graft copolymer of polyethylene terephthalate with acrylic acid has been prepared by γ-irradiation. Thermal analysis in air and nitrogen has been made on the original polymer, the acidic copolymer and also on the sodium, lead and cupric salts of the copolymer. In addition to thermal degradation, all samples suffer thermo-oxidative degradation in air in the region of the melting point. The weight loss in air and in nitrogen for all the copolymers at this temperature exceeds that of the ungrafted polymer.     

A delicate ionizable-group effect on self-assembly and thermogelling of amphiphilic block copolymers in water

A carboxyl-capped PLGA-PEG-PLGA block copolymer (PLGA: poly(d,l-lactic acid-co-glycolic acid), PEG: poly(ethylene glycol)) was synthesized, and its self-assembly and thermogelling behaviors in water were studied at different pH values. While the aqueous solution of the virgin PLGA-PEG-PLGA block copolymer with the composition in this paper did not undergo sol-gel transition, that of the end-capped derivative exhibited four macroscopic states, sol, turbid sol, physical gel, and precipitate, dependent upon temperature and pH. Especially between pH 4.5 and 5.0, a concentrated aqueous system underwent sol-gel-(turbid sol)-precipitate transitions upon increase of temperature. Complex of dissociation constant pK_a of weak-acid groups on the micelle surfaces was illustrated. Dynamic light scattering, hydrophobic dye solubilization, transmission electron microscopy, NMR, and potentiometric titration were used to examine the relationship between ionization of the end groups of the polymer chains on the molecular level, micellization of the amphiphilic block copolymers on the supermolecular level, and physical gelation on the macroscopic level. The present research reveals the complex of the multi-scale self-assembly of amphiphilic polymer ionomers in a selective solvent.     

Surfactant assisted selective confinement of carbon nanotubes functionalized with octadecylamine in a poly(styrene-b-isoprene-b-styrene) block copolymer matrix

We report how dodecanethiol (DT) surfactant can be used as a good dispersant to solubilize octadecylamine functionalized single-walled carbon nanotubes (ODA-SWCNTs) in order to confine them in the polystyrene phase of the polystyrene-b-polyisoprene-b-polystyrene (SIS) block copolymer matrix. It has been also demonstrated how the block copolymer matrix is not able to self-assemble in ordered morphology when the ODA-SWCNTs are not modified with the surfactant. DT assisted confinement of carbon nanotubes into the PS phase causes not only the nanostructuration of the host polymer matrix but also switches the self-assembled nanostructure from ordered cylinders in the case of neat SIS to a self-assembled lamellar nanostructure.     

两亲性苯乙烯嵌段共聚物的合成及结构表征

以α,α'-二甲基-α-乙酸-三硫代碳酸酯(BDATC)为链转移剂,采用可逆-加成-断裂链转移(RAFT)自由基聚合方法合成了末端带有—COOH官能团的两亲性嵌段共聚物聚苯乙烯-b-聚甲基丙烯酸聚乙二醇单甲醚-b-聚苯乙烯(PSt-b-POEOMA-b-PSt),这种含有亲水性端基的嵌段共聚物可以自组装成核-壳结构的纳米微粒,用于载药高分子的模板研究。利用FTIR、1HNMR、GPC对产物结构进行表征,用热失重(TG)和差示扫描量热(DSC)的方法研究了3种不同比例的嵌段共聚物的热性能。实验结果表明,通过RAFT聚合方法得到了所设计的嵌段共聚物,相对分子质量(简称分子量,下同)分布1.35左右;嵌段共聚物的热稳定性较好,通过玻璃化转变温度(Tg)的变化推测出嵌段共聚物中两种嵌段比例对两嵌段相容性的影响。     

Drug‐releasing behavior of MPEG/PLA block copolymer micelles and solid particles controlled by component block length

Three series of poly(ethylene glycol)methyl ether (MPEG)/poly(lactic acid) (PLA) block copolymer systems, composed of MPEG in the molecular weights of 2000, 5000, and 750 g/gmol, respectively, and PLA in different molecular weights were synthesized. The chemical structure and physical properties were investigated using FTIR, NMR, DSC, TGA, and GPC. Different crystallization and melting transition behavior were observed according to the variation of the component block length. Either nano‐sized micelles or solid particles were formed in water, depending on the component block length and its ratio. The mean diameter of spherical drug carriers was controlled by the preparation conditions and was characterized using DLS and SEM. Indomethacin was loaded into nano‐sized spherical polymer carriers. The releasing rates were significantly affected by not only the sizes but also by the physical state of the drug carriers in the media, resulting from the difference in the component block length and the molecular entanglement of the PLA cores. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 435–445, 2002     

Preparation and characterization of a polyphenylene ether and Nylon-6 block copolymer

Summary A block copolymer of PPO^®(1) and Nylon-6 was prepared through modification of the hydroxyl end group of the polyphenylene ether (PPE) with cyanuric chloride or 4,4-difluorobenzophenone and subsequent anionic polymerization of -caprolactam using the modified PPE as the promoter. The pure copolymer was isolated by selective solvent extraction, using chloroform to remove PPE homopolymer and unreacted -caprolactam, and formic acid to remove Nylon-6 homopolymer. The copolymer has two melting points indicative of the Nylon and PPE segments. Its composition has been determined by carbon-13 NMR and elemental analysis.     

Synthesis of poly(ethylene glycol-b-styrene) block copolymers by reverse atom transfer radical polymerization

Reverse atom transfer radical polymerization (RATRP) of styrene (S) was carried out in bulk using polyazoester prepared by the reaction of polyethylene glycol with molecular weight of 3000 and 4,4′-azobis(4-cyanopentanoyl chloride) as initiator and CuCl₂/2,2′-bipyridine (bpy) catalyst system to yield poly(ethylene glycol-b-styrene) block copolymer. The block copolymers were characterized ¹H NMR, FT-IR spectroscopy and GPC. The ¹H NMR, and FT-IR spectra showed that formation of poly(ethylene glycol-b-styrene) block copolymer. The polydispersities of block copolymers were observed between from 1.49 and 1.98 GPC measurements.     

Asymmetric morphology from an organic/organometallic block copolymer

Block copolymer self-assembly is a burgeoning subject in polymer and materials science driven by both fundamental and applied inspirations. Whereas the vast majority of block copolymer studies have focused on highly symmetric morphologies, here we report the first observation of an unusual asymmetric cylindrical phase in thick films of an organic/organometallic block copolymer, poly(styrene-block-ferrocenyldimethylsilane) (PS-b-PFS). Microscopy and X-ray scattering data establish the lack of symmetry in this structure and reveal an unusual 3-D network organization. Following selective removal of the PS matrix, the remaining nanoporous film has characteristics of potential value in separation applications such as substantial interconnection (mechanical strength), uniform pore size, and chemical and physical stability.     

DPE法合成双亲性丙烯酸酯嵌段共聚物及用于颜料分散剂的研究

以1,1-二苯基乙烯（DPE）为分子量调节剂,偶氮二异丁腈（AIBN）为引发剂进行甲基丙烯酸丁酯（BMA）的可控自由基聚合（DPE法）。研究了溶剂、DPE用量及反应温度对于聚合的影响,得到分子量分布较窄（PDI=1.43）的含有DPE半醌式休眠种结构的聚甲基丙烯酸丁酯（PBMA）。以PBMA为引发剂引发甲基丙烯酸二甲氨基乙酯（DMAEMA）聚合,得到分子量分布较窄的（PDI=2.0）双亲性嵌段共聚物（PBMA-b-PDMAEMA）。核磁共振氢谱（¹H NMR）测得共聚物组成与GPC测试结果相近。差示扫描量热分析（DSC）测试表明嵌段共聚物在11℃和35℃处有两个玻璃化转变温度。色浆的流变和粒径测试及漆膜性能测试表明,将所得双亲性嵌段共聚物作为酞菁蓝颜料分散剂,可以明显提高酞菁蓝颜料在丙烯酸酯树脂中的分散效率。     

Phase behavior of poly(ether urethane)-nylon 6 block copolymer

Poly(ether urethane) (PEU)-Nylon 6 block copolymer film prepared via melt pressing and subsequent quenching in liquid nitrogen exhibited a one-phase structure due to the specific interaction between urethane groups in the PEU block and the amide groups in Nylon 6 block through hydrogen bonding. Contrary to this, the solvent cast film showed a microphase separated structure which had risen from the poor solubility characteristics of the PEU block in the solvent. However, by heat treatment, the mutual miscibility of the block copolymer increased as a result of the hydrogen bonding formation. The block copolymer and Nylon 6 binary blend showed that these two polymers are compatible over the entire composition range mainly due to the specific interactions between the urethane and the amide groups in the blend through hydrogen bonding. The block copolymer in the ternary blend which consists of polyrethane (PU), Nylon 6, and the block copolymer prepared by melt extrusion was soluble in either of the PU and Nylon 6 homopolymers, inducing a homogenizing effect. © 1994 John Wiley & Sons, Inc.