We have been able to prepare a molecular complex between the poly(ethylene oxide) block of a poly(ethylene)-b-poly(ethylene-alt-propylene)-b-poly(ethylene oxide) triblock copolymer and p-nitrophenol (PNP). The composition of the copolymer employed was: 24% PE, 57% PEP and 19% PEO in weight percent. The pure copolymer exhibited a non-conventional thermal behavior since the PEO block displayed a fractionated crystallization process during cooling. The PEO block/PNP complex did not show any apparent crystallization during cooling, instead cold crystallization during heating was observed and an approximately 30°C increase in melting point as compared to the neat PEO block within the copolymer. This caused an overlap in the melting regions of the PE block and the PEO block/PNP complex. The self-nucleation of the PE-b-PEP-b-PEO/PNP complex is very different from that of the neat triblock copolymer. An increased capacity for self-nucleation of the PEO block was produced by the complexation with PNP and therefore the three self-nucleation domains were clearly encountered for both the PE block and for the PEO block/PNP complex. Self-nucleation was able to show that the two crystallizable blocks can be self-nucleated and annealed in an independent way, thereby ascertaining the presence of separate crystalline regions in the triblock copolymer. Through the use of PNP, both the crystallinity and the melting point of the PE-b-PEP-b-PEO block copolymer employed here can be substantially increased. Similar results were obtained by complexation of the same ABC triblock copolymer with resorcinol. 相似文献
Effects of adding a small amount of poly(methyl methacrylate)-block-poly(vinyl acetate) (PMMA-b-PVAc) to poly(methyl methacrylate)/poly(vinyl acetate) (PMMA/PVAc) blends with a lower critical solution temperature (LCST) phase diagram on the kinetics of late-stage spinodal decomposition (SD) were investigated by time-resolved light scattering at 160°C. It is found that the coarsening process of the structure was slowed down or accelerated upon addition of PMMA-b-PVAc depending on the composition of the block copolymer and the blend. The effect of the block copolymer on the domain size were interpreted as compatibilizing and incompatibilizing effects of the block copolymer on PMMA/PVAc blends based on the evaluation of changes in the stability limits of PMMA/PVAc with the addition of block copolymer using random phase approximation (RPA). 相似文献
A novel glycopeptide-containing block copolymer, poly[O-(tetra-O-acetyl-β-D -glucopyranosyl)-L -serine]-block-poly(2-methyl-2-oxazoline) ( 5 ), was synthesized by mutual termination of living polymerizations of a sugar-substituted α-amino acid N-carboxyanhydride (NCA) ( 1 ) and 2-methyl-2-oxazoline ( 3 ). 5 was deacetylated to provide the glycopeptide-polyoxazoline block copolymer, poly[O-(β-D -glucopyranosyl)-L -serine]-block-poly(2-methyl-2-oxazoline) ( 6 ). 相似文献
Macrocyclic poly(styrene-b-butadiene) (SB) block copolymers were prepared by coupling a living poly(styrene-b-butadiene-b-styrene) (SBS) block copolymer using a living coupling agent, 1,3-bis(1-phenylethylenyl)benzene (DDPE), or a difunctional electrophile, dimethyldichlorosilane. The living poly(styrene-b-butadiene-b-styrene) block copolymer was generated from an addition product of sec-butyllithium and DDPE. A living heteroarmed star block copolymer has been prepared by coupling two moles of monolithium polystyrene with one mole of DDPE followed by reinitiation and polymerization of the butadiene monomer. The dilithium 4-armed star block copolymer was then coupled using dimethyldichlorosilane to form a cyclic polybutadiene with two attached polystyrene branches. 相似文献
The pH-responsive double hydrophilic block copolymer poly(ethylene glycol)-b-poly(methacylic acid-co-4-vinyl benzylamine hydrochloride salt) (PEG-b-PMAA/PVBAHS) was synthesized. A series of PEG-b-PMAA/PVBAHS with different molecule weights and compositions were characterized by IR, 1H-NMR, elemental analysis and TGA. With different MAA/VBAHS ratio, the PEG-b-PMAA/PVBAHS copolymers had the different isoelectric point (IEP). Supermolecular structures of the block copolymers could be formed by the interionic interactions at different solution pH. Experiment results showed that the structures of the pH-responsive copolymers in aqueous solution could be changed at different pH environments. The aggregation of this double hydrophilic block copolymer in aqueous solution was determined by both of solution pH and copolymer composition. 相似文献
The synthesis of the poly(para-phenyleneethynylene)-block-poly(ethylene oxide) block copolymer (PPE-b-PEO) ( 1 ) via condensation of endfunctionalized poly(para-phenyleneethynylene) (PPE) ( 5 ) and poly(ethylene oxide) monomethyl ether (PEO) is reported. This is achieved by the initial synthesis of a PPE homopolymer with quantitative terminal functionalization, as proven by 1H NMR and field desorption mass spectrometry (FD-MS). Reaction of the latter with PEO affords the block copolymer 1 , which was characterized by 1H NMR spectroscopy, FD-MS and gel permeation chromatography (GPC). Furthermore it is shown that matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) is a suitable method to investigate PPE-b-PEO with respect to molecular weights and copolymer composition. 相似文献
To prepare a thin film, the block copolymer poly(TMCM-MOE3OM)-b-PTMC was prepared with different segment ratios of hydrophilic moiety. The glass transition temperature of poly(TMCM-MOE3OM)-b-PTMC decreased as the content of TMCM-MOE3OM increased as expected, and it was confirmed that the graft oligo(ethylene glycol) (OEG) affected intermolecular interaction. The polymers grafted with OEG showed a thermoresponsive property, which can be expected to be applied to materials triggered by temperature. A thin film was prepared by mixing block copolymer and cilostazol as a drug, and the distribution of cilostazol was observed. It was confirmed that cilostazol was uniformly distributed on the thin film and that local sustained release could be avoided at the time of elution. The eluting behavior of the thin film from the substrate was apparently affected on the segment ratio of the block copolymer. When the thin film was immersed in PBS, the eluting rate increased as the segment ratio of TMCM-MOE3OM in the block copolymer increased. As a result, it is possible to control the eluting rate by changing the ratio of the hydrophilicity and the hydrophobicity of the block copolymer, contributing to the creation of a new coating material containing cilostazol. 相似文献
The micellization behavior of novel tertiary amine methacrylate-based ABA type triblock copolymers formed by poly[2-(dimethylamino)ethyl methacrylate] [PDMA] middle block and poly[2-(diethylamino)ethyl methacrylate] [PDEA] or poly[2-(diisopropylamino)ethyl methacrylate] [PDPA] side blocks, PDPAm-b-PDMAn-b-PDPAl, and PDEAm-b-PDMAn-b-PDEAl was investigated. Both types of triblock copolymers were water-soluble and had potential for various applications due to their self-assembled and the bottom-up nanoscale micellar construction. The micellar aggregations of the triblock copolymers in aqueous solutions with varying comonomer ratios, molecular weights, temperatures, and pH values were investigated by small-angle X-ray scattering and dynamic light scattering. Compact micellar aggregations were obtained as 0.5 weight percent solutions at 20–21°C and pH 8.67 to 9.05, and characterized as polydispersed spherical core-shells. One group of triblock copolymer micelles had PDPA-cores with radii from 18 to 21 Å and PDMA-shell thicknesses of 89–105 Å, whereas the other group had PDEA-core spherical micelles with core radii of 60–62 Å and a PDMA-shell thicknesses of 64–66 Å. 相似文献
This study involves the investigation of the complexation ability of poly(2-[dimethylamino]ethyl methacrylate)-b-poly(hydroxypropyl methacrylate) (PDMAEMA-b-PHPMA) amphiphilic pH and thermoresponsive block copolymers, and their quaternized counterparts QPDMAEMA-b-PHPMA, toward short DNA in aqueous solutions. The PDMAEMA-b-PHPMA amphiphilic block copolymers present various self-assembly characteristics when inserted into aqueous media, depending on the composition, the solubilization protocol, the acidity and the temperature of the aqueous media. Copolymer aggregates-DNA interactions and nanostructure formation after complexation are investigated by dynamic light scattering and intensity measurements in aqueous solutions in a fixed temperature range, utilizing two different solubilization protocols for the copolymers. Ethidium bromide assays by fluorescence spectroscopy and ζ-potential measurements were also utilized to investigate the structure and properties of the DNA/copolymer polyplexes. The interpretation of such physicochemical characterization provides extra comprehension of the novel (Q)PDMAEMA-b-PHPMA copolymers self-assembly characteristics and assesses their ability for DNA complexation, stabilization, and delivery. 相似文献
Complexation ability of poly(2-(dimethylamino)ethyl methacrylate)-b-poly(hydroxy propyl methacrylate) (PDMAEMA-b-PHPMA) amphiphilic doubly thermo-responsive block copolymers, and their quaternized counterparts QPDMAEMA-b-PHPMA, toward bovine serum albumin (BSA) is studied in aqueous solutions. The PDMAEMA-b-PHPMA amphiphilic block copolymers self-assemble in nanostructured aggregates with PDMAEMA coronas having different inner structure and micro-polarity depending on the solubilization protocol utilized when inserted in aqueous media. By incorporating different BSA concentrations, we investigate the copolymer–protein interactions by light scattering measurements in aqueous solutions in a broad temperature range, utilizing different solubilization protocols for the copolymers. Fluorescence spectroscopy and ζ-potential measurements were also utilized to investigate the structure and properties of the copolymer/protein complexes formed in each case. Such knowledge may lead to a better understanding of the inner structure and micro polarity of the nanostructured aggregates formed by the novel (Q)PDMAEMA-b-PHPMA copolymers, along with their potential abilities in nanocarrier formation, protein complexation, stabilization, and delivery. 相似文献
ABSTRACT One kind of poly(methyl methacrylate [MMA]-block-2-hydroxyethyl methacrylate [HEMA]) block copolymer and two kinds of poly[MMA1-block-(MMA-co-HEMA)] block-random copolymers were synthesized by atom transfer radical polymerization. Then, poly(methyl methacrylate) [PMMA]-silica nano composites were synthesized by blending perhydropolysilazane (PHPS: NN-110) and block or block-random copolymers in 1,4-dioxane and casting the blend solutions. All composite films were transparent. Silica and organic domains were microphase separated in the composites. The effects of PHEMA content and blend ratio of PHPS to hydroxyl group on the microphase separation were investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The thermal properties of the composites were investigated by differential scanning calorimetry (DSC) and thermal gravitic analysis (TGA). 相似文献
Summary: Based on a hydrophilic poly(ethylene oxide) macroinitiator (PEOBr), a novel amphiphilic diblock copolymer PEO‐block‐poly(11‐(4‐cyanobiphenyloxy)undecyl) methacrylate) (PEO‐b‐PMA(11CB)) was prepared by atom transfer radical polymerization (ATRP) using CuCl/1,1,4,7,10,10‐hexamethyltriethylenetriamine as a catalyst system. An azobenzene block of poly(11‐[4‐(4‐butylphenylazo)phenoxyl]undecyl methacrylate) was then introduced into the copolymer sequence by a second ATRP to synthesize the corresponding triblock copolymer PEO‐b‐PMA(11CB)‐b‐PMA(11Az). Both of the amphiphilic block copolymers had well‐defined structures and narrow molecular‐weight distributions, and exhibited a smectic liquid‐crystalline phase over a wide temperature range.
The amphiphilic triblock copolymer synthesized here. 相似文献
The preparation of some unique block copolymers and block copolymer particles via radical heterophase polymerization is described. Special emphasis is placed on double hydrophilic block copolymers such as poly(styrene sulfonic acid)-b-poly(methacrylic acid) diblock copolymer and double hydrophilic block copolymer particles consisting of both hydrophilic shells and cross-linked hydrophilic cores. Examples are given for the application of such particles as adsorbents, nano-reactors for chemical synthesis, and as colloidal stabilizers in both heterophase polymerization and biomineralization reactions. 相似文献