Synthesis and characterization of novel thermo‐ and pH‐responsive copolymers based on amphiphilic polyaspartamides

Novel amphiphilic, thermo‐ and pH‐responsive polyaspartamides showing both double‐responsive (pH and temperature) behavior and a sol‐gel transition were prepared and characterized. The polyaspartamide derivatives were synthesized by the successive aminolysis reactions of polysuccinimide using both hydrophobic N‐alkylamine (laurylamine, octylamine, hexylamine) and hydrophilic N‐isopropylethylenediamine. The composition of each component was analyzed by ¹H NMR. At the intermediate composition range, the system showed a lower critical solution temperature behavior in water. The transition temperature (pH dependent) could be modulated by changing the alkyl chain length and graft composition. The temperature dependence of the nanoparticle size distribution of the polyaspartamide derivatives was also examined. The critical micelle concentration of the copolymers in a phosphate‐buffered saline (pH 7.4) solution ranged from 6 to 20 μg/L. In addition, physical gelation, i.e., a sol‐gel transition, was observed in a concentrated solution. These novel double‐responsive and injectable hydrogels have potential biomedical applications such as drug delivery systems and tissue engineering. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

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 %。     

Synthesis of biodegradable poly(trans-4-hydroxy-N-benzyloxycarbonyl-l-proline)-block-poly(ε-caprolactone) copolymers and micellar characterizations

A series of novel types of diblock poly(trans-4-hydroxy-N-benzyloxycarbonyl-l-proline)-block-poly(ε-caprolactone) (PHpr10-b-PCL) copolymers were synthesized by ring-opening polymerization from macroinitiator poly(trans-4-hydroxy-N-benzyloxycarbonyl-l-proline) (PHpr10) and ε-caprolactone (ε-CL) in the presence of organocatalyst dl-lactic acid (dl-LA). The M_n of the copolymers increased from 3370 to 19,040 g mol⁻¹ with the molar ratio (10-100) of ε-CL to PHpr10. These products were characterized by differential scanning calorimetry (DSC), ¹H NMR, and gel permeation chromatography. According to DSC, the glass-transition temperature (T_g) of the diblock copolymers depend on the molar ratio of monomer/initiator that were added. The hydrolytic degradation behavior of PHpr-b-PCLs was evaluated from weight-loss measurements and the change of M_n and M_w/M_n. With higher PCL contents resulted in a slower weight loss, while having a higher molecular weight loss percentage. Their micellar characteristics in an aqueous phase were investigated by fluorescence spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The block copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 1.33-4.22 mg L⁻¹. The micelles exhibited a spindly shape and showed a narrow monodisperse size distribution. The obtained micelles have a relatively high drug-loading of about 26% when the feed weight ratio of amitriptyline hydrochloride (AM) to polymer was 1/1. An increase of molecular weight and hydrophobic components in copolymers produced a higher CMC value and greater loading efficiencies were observed.     

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。     

Reversible sol–gel transitions in aqueous solutions of N‐isopropylacrylamide ionic copolymers

Ionic copolymers of N‐isopropylacrylamide (NIPA) exhibiting sol–gel transitions in aqueous solutions were investigated. The studies were aimed at understanding of the structure–property relationship in the design of injectable, in situ forming gels for potential biomedical applications in delivery of therapeutics and tissue engineering. Aqueous solutions of NIPA ionic copolymers were found to flow freely at ambient temperatures and formed soft gels with controlled syneresis above 32 °C, the lower critical solution temperature of NIPA. The sol–gel transitions and temperature‐dependent properties of the resulting gels were analyzed using dynamic rheometry and ultraviolet and infrared spectrometry, and were found to be controlled by the molecular weight and composition of copolymers, ionization state of comonomers and composition of aqueous solvent. Copyright © 2008 Society of Chemical Industry     

Synthesis and characterization of biodegradable and biocompatible amphiphilic block copolymers bearing pendant amino acid residues

Polylactide (PLA)-based biodegradable and biocompatible amphiphilic block copolymers bearing pendant amino acid residues were synthesized through a relatively easy and efficient way. The composition and structure of these copolymers were characterized by gel permeation chromatography (GPC) and ¹H nuclear magnetic resonance (¹H NMR) spectroscopy. The self-assembly behavior of the copolymers was investigated by fluorescence (FL), dynamic light scattering (DLS), and transmission electron microscope (TEM). It was shown that aggregates less than 100 nm in average size were formed by these copolymers, which changed from micelles to vesicles with the variation of the block length. In addition, the in vitro cytotoxicity of these copolymers was determined and compared with that of PEO-b-PLA in the presence of Bel-7402 cells. The result suggested that the block copolymers PAGE/cys-b-PLA exhibited better biocompatibility. Therefore, these PLA-based copolymers are expected to find promising applications in drug delivery or tissue engineering.     

The Effect Acetic Acid has on Poly(N-Vinylcaprolactam) LCST for Biomedical Applications

The aim of this research was to synthesize Poly(N-vinylcaprolactam) (PNVCL) with the incorporation of hydrophilic acetic acid with thermosensitive N–vinylcaprolactam for potential drug delivery applications. Preparation of the heterogeneous mixture involved photopolymerization of a combination of N–vinylcaprolactam and acetic acid at different ratios. By altering the feed ratio, hydrogels were synthesized to have lower critical solution temperature close to physiological temperature. This ability to shift the phase transition temperature of PNVCL provides excellent flexibility in tailoring transitions to suit physiological temperature, inheriting great potential in drug delivery.     

Synthesis of biodegradable and biocompatible ABC triblock copolymers

A facile approach is offered to synthesize well‐defined amphiphilic ABC triblock copolymers composed of poly(ethylene glycol) monomethyl ether (MPEO) as A block, poly(L ‐lysine) (PLLys) as B block, and poly(ε‐caprolactone) (PCL) as C block by a combination of ring‐opening polymerization (ROP) and click reactions. The propargyl‐terminated poly(Z‐L ‐lysine)‐block‐poly(ε‐caprolactone) (MPEO‐PzLLys‐PCL) diblock copolymers were synthesized via the ring‐opening polymerization of N^ε‐carbobenzoxy‐L ‐lysine N‐carboxyanhydride (Z‐L ‐Lys NCA) in DMF at room temperature using propargyl amine as an initiator and the resulting amino‐terminated poly(Z‐L ‐lysine) then used in situ as a macroinitiator for the polymerization of ε‐caprolactone in the presence of stannous octoate as a catalyst. The triblock copolymers poly(ethylene glycol) monomethyl ether –block‐poly(Z‐L ‐lysine)‐block‐poly(ε‐caprolactone) (MPEO‐PzLLys‐PCL) were synthesized via the click reaction of the propargyl‐terminated PzLLys‐PCL and azido‐terminated poly(ethylene glycol) monomethyl ether (PEO‐N₃) in the presence of CuBr and 1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) catalyst system. After the removal of Z groups of L ‐lysine units, amphiphilic and biocompatible ABC triblock copolymers MPEO‐PLLys‐PCL were obtained. The structural characteristics of these ABC triblock copolymers and corresponding precursors were characterized by NMR, IR, and GPC. These results showed the click reaction was highly effective. Therefore, a facile approach is offered to synthesize amphiphilic and biocompatible ABC triblock copolymers consisting of polyether, polypeptide and polyester. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermoplastic hydrogel based on pentablock copolymer consisting of poly(γ‐benzyl L‐glutamate) and poloxamer

A thermoplastic hydrogel based on a pentablock copolymer composed of poly(γ‐benzyl L ‐glutamate) (PBLG) and poloxamer was synthesized by polymerization of BLG N‐carboxyanhydride, which was initiated by diamine‐terminated groups located at the ends of poly(ethylene oxide) (PEO) chains of the poloxamer, to attain a new pH‐ and temperature‐sensitive hydrogel for drug delivery systems. Circular dichroism measurements in solution and IR measurements in the solid state revealed that the polypeptide block existed in the α‐helical conformation, as in the PBLG homopolymer. The intensity of the wide‐angle X‐ray diffraction patterns of the polymers depended on the poloxamer content in the copolymer and showed basically similar reflections to the PBLG homopolymer. The melting temperature (T_m) of the poloxamer in the copolymer was reduced with an increase of the PBLG block in comparison with the T_m of the poloxamer, which is indicative of a thermoplastic property. The water contents of the copolymers were dependent on the poloxamer content in the copolymers, for example, those for the GPG‐2 (48.7 mol % poloxamer) and GPG‐1 (57.5 mol % poloxamer) copolymers were 31 and 41 wt %, respectively, indicating characteristics of a polymeric hydrogel. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2649–2656, 2003     

Synthesis of amphiphilic temperature‐sensitive poly(N‐isopropylacrylamide)‐block‐poly(tetramethylene carbonate) block copolymers and micellar characterization

Amphiphilic thermally sensitive poly(N‐isopropylacrylamide)‐block‐poly(tetramethylene carbonate) block copolymers were synthesized by ring‐opening polymerization of tetramethylene carbonate with hydroxyl‐terminated poly(N‐isopropylacrylamide) (PNiPAAm) as macro‐initiator in the presence of stannous octoate as catalyst. The synthesis involved PNiPAAm bearing a single terminal hydroxyl group prepared by telomerization using 2‐hydroxyethanethiol as a chain‐transfer agent. The copolymers were characterized using ¹H NMR and Fourier transform infrared spectroscopy and gel permeation chromatography. Their solutions show reversible changes in optical properties: transparent below the lower critical solution temperature (LCST) and opaque above the LCST. The LCST depends on the polymer composition and the media. Owing to their amphiphilic characteristics, the block copolymers form micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range 1.11–22.9 mg L^?1. Increasing the hydrophobic segment length or decreasing the hydrophilic segment length in the amphiphilic diblock copolymers produces lower CMCs. A core‐shell structure of the micelles is evident from ¹H NMR analyses of the micelles in D₂O. Transmission electron microscopic analyses of micelle morphology show a spherical structure of both blank and drug‐loaded micelles. The blank and drug‐loaded micelles have an average size of less than 130 nm. Observations show high drug‐entrapment efficiency and drug‐loading content for the drug‐loaded micelles. Copyright © 2010 Society of Chemical Industry     

Preparation of liquid‐filled micelles based on an amphiphilic triblock copolymer

A series of novel amphiphilic triblock poly(ethylene glycol)‐b‐poly(2‐aminoethyl methacrylate hydrochloride)‐b‐poly(heptadeca‐fluorodecyl acrylate) (PEG‐b‐PAEMA‐b‐PHFDA) comprised of two hydrophilic PEG and PAEMA segments and one hydrophobic PHFDA segment was designed and synthesized. The structure of the triblock copolymer was characterized by ¹H‐NMR and GPC analysis. The amphiphilic triblock copolymer was capable of self‐assembling into liquid‐filled micelles that consisted of PHFDA and liquid perfluorocarbons (PFCs) as the core and PEG as outer shell. PAEMA can be used as cross‐linking sites to increase the stability of the liquid‐filled micelles. The shape, size, and Acoustic properties of the obtained liquid‐filled micelles were investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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.     

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 applications of triblock and multiblock copolymers using telechelic oligopropylene

Isotactic polypropylene (iPP)-polystyrene (PS) and iPP-poly(methyl methacrylate) (PMMA) multiblock copolymers were synthesized by atom transfer radical coupling (ATRC) of PS-iPP-PS and PMMA-iPP-PMMA triblock copolymers obtained by atom transfer radical polymerization (ATRP) of styrene (St) and methyl methacrylate (MMA), respectively, using α,ω-dibromoisobutyrateoligopropylene (iPP-Br) as a bifunctional macroinitiator. The iPP-Br was prepared by hydroxylation and subsequent esterification of telechelic oligopropylene having terminal vinylidene double bonds at both ends obtained by controlled thermal degradation of iPP. ATRP of St and (meth) acrylic monomers using iPP-Br formed the corresponding triblock copolymers. It was confirmed that the PMMA-iPP-PMMA triblock copolymer was effective as the compatibilizer for the iPP/PMMA blend. An iPP-PS multiblock copolymer (M_n: 25?000 g/mol and M_w/M_n: 4.1) was prepared by ATRC of PS-iPP-PS triblock copolymer (M_n: 8900 g/mol and M_w/M_n: 1.3). ATRC with St of PMMA-iPP-PMMA triblock copolymer (M_n: 13?000 g/mol and M_w/M_n: 1.4) provided an iPP-PMMA multiblock copolymer containing St chains (M_n: 39?000 g/mol and M_w/M_n: 2.8).     

Synthesis and characterization of poly(oxyethylene)–poly(caprolactone) multiblock copolymers

Novel poly(oxyethylene)/poly(caprolactone) POE/PCL copolymers were synthesized by step growth polymerization of poly(ε-caprolactone) diols and poly(ethylene glycol) diacids using dicyclohexylcarbodiimide as coupling agent. The reaction was performed at room temperature and yielded multiblock copolymers with predetermined POE and PCL block lengths. The resulting copolymers were characterized by various analytical techniques including SEC, IR, ¹H NMR, DSC and X-ray diffractometry. Data showed that the properties of these polymers can be modulated by adjusting the chain lengths of the macromonomers. In particular, one or two crystalline structures can exist within the copolymers of various crystallinities. © 1998 SCI.     

Bisphenol-A polycarbonate/polydimethylsiloxane multiblock copolymers. I. Synthesis and characterization

Aminopropyl-terminated polydimethylsiloxane (PDMS)-bisphenol-A polycarbonate block copolymers were synthesized by interfacial phosgenation reaction of 2,2-bis(4-hydroxyphenyl) propane (BPA) and aminopropyl-terminated PDMS. A new synthetic procedure shows better conversion yield of PDMS oligomer. IR, ¹H, ¹³C, and ²⁹Si nuclear magnetic resonance spectra were used to identify the exact chemical structures of the PDMS-PC block copolymers. The conversions of PDMS of these copolymers were ∼ 90% and independent of the PDMS content. The intrinsic viscosities, IV, [γ] studied were in the range between 0.23 and 2.25 dL/g in dichloromethane at 25°C with different reaction conditions. The intrinsic viscosity and the glass transition temperature decreased with increasing PDMS content at the same reaction temperature, while the melting flow indices increase with increasing PDMS content. Transparent and colorless films, which showed good oxygen-to-nitrogen permselectivity, could be cast from dichloromethane. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 57–66, 1997     

Nanostructuring compatibilizers of block copolymers for organic photovoltaics

The performance and stability of organic photovoltaic (OPV) devices based upon bulk heterojunction blends of donor and acceptor materials have been shown to be highly dependent on the morphology of the active layer. Block copolymers, which naturally self‐assemble into periodic ordered nanostructures, can be utilized in diverse ways to control morphology on a length scale relevant for charge separation, recombination and transportation, which makes them promising candidates for high performance and thermally stable OPV devices. This minireview presents a brief statistical discussion of inter‐study correlations and a summary of past interfacial research on block copolymer nanostructuring compatibilizers for OPVs. © 2013 Society of Chemical Industry     

In situ gel forming systems of poloxamer 407 and hydroxypropyl cellulose or hydroxypropyl methyl cellulose mixtures for controlled delivery of vancomycin

Poloxamers are a family of triblock copolymers consisting of two hydrophilic blocks of polyoxyethylene separated by a hydrophobic block of polyoxypropylene, which form micelles at low concentrations and form clear thermally reversible gels at high concentrations. The objective of this study was to develop an in situ gel forming drug delivery system for vancomycin using the minimum possible ratio of poloxamer 407 (P407). Decreasing the concentration of poloxamer could reduce the risk of hypertriglyceridemia induction. Different additives were added to the poloxamer formulations. It was observed that among different additives, hydroxypropyl methyl cellulose (HPMC) and hydroxypropyl cellulose (HPC) can decrease poloxamer concentration required to form in situ gelation from 18 to 10%. The dynamic viscoelastic properties of the samples were determined. Both the storage modulus and the loss modulus of the samples increased abruptly as the temperature passed a certain point. The gelling temperature was in the order of P407 : HPC (10 : 10 w/w) < P407 : HPMC (10 : 10 w/w) < P407 : HPMC (15 : 5 w/w) < P407 : HPC (15 : 5 w/w). Drug release rate could be controlled by changing the type and ratio of additives as well as the amount of drug loaded. It can be concluded that combining P407 and cellulose derivatives could be a promising strategy for preparation of thermally reversible in situ gel forming delivery systems with low poloxamer concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polyimide‐polyurethane/urea block copolymers for highly sensitive humidity sensor with low hysteresis

Polyimide (PI)‐polyurethane‐urea (PU) block copolymers (PI‐PU75/25, PI‐PU50/50, and PI‐PU25/75) were prepared by reaction between anhydride‐terminated poly(amic acid) prepolymers with various number‐average degree of polymerization = 73/49/25) and isocyanate‐terminated urethane‐urea prepolymers with various (11/21/31) to obtain high performance capacitive humidity sensors. Pure PI and PU were also prepared to compare with PI‐PU copolymers. This study examined the effect of PU content on the water absorption %/water vapor transmission rate, thermal and mechanical properties and sensing properties of PI‐PU block copolymers. The thermal stability and mechanical properties of the copolymer decreased markedly with increasing PU content. The sensitivity of sensor increased sharply with increasing PU content from 0 to 25 wt %, and then increased a little. The hysteresis of sensor decreased sharply with increasing PU content up to 50 wt %, and then decreased a little. These results demonstrate the apparent upside of using two copolymers (PI‐PU75/25 and PI‐PU50/50) compared to using pure PI, in terms of sensor performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44973.