Showing papers on "Copolymer published in 1998"
TL;DR: An exceptionally high electrostrictive response was observed in electron-irradiated poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer, suggesting that the electron irradiation breaks up the coherent polarization domain in normal ferroelectric P( VDF- TrFE)Copolymer into nanopolar regions that transform the material into a relaxor ferroElectric.
Abstract: An exceptionally high electrostrictive response ( approximately 4 percent) was observed in electron-irradiated poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer. The material exhibits typical relaxor ferroelectric behavior, suggesting that the electron irradiation breaks up the coherent polarization domain (all-trans chains) in normal ferroelectric P(VDF-TrFE) copolymer into nanopolar regions (nanometer-size, all-trans chains interrupted by trans and gauche bonds) that transform the material into a relaxor ferroelectric. The expanding and contracting of these polar regions under external fields, coupled with a large difference in the lattice strain between the polar and nonpolar phases, generate an ultrahigh strain response.
1,451 citations
TL;DR: It was demonstrated that polymeric supramolecular nanostructures with several length scales allow straightforward tailoring of hierarchical order-disorder and order-order transitions and the concurrent switching of functional properties.
Abstract: It was demonstrated that polymeric supramolecular nanostructures with several length scales allow straightforward tailoring of hierarchical order-disorder and order-order transitions and the concurrent switching of functional properties. Poly(4-vinyl pyridine) (P4VP) was stoichiometrically protonated with methane sulfonic acid (MSA) to form P4VP(MSA)1.0, which was then hydrogen-bonded to pentadecylphenol. Microphase separation, re-entrant closed-loop macrophase separation, and high-temperature macrophase separation were observed. When MSA and pentadecylphenol were complexed to the P4VP block of a microphase-separated diblock copolymer poly[styrene-block-(4-vinyl pyridine)], self-organized structures-in-structures were obtained whose hierarchical phase transitions can be controlled systematically. This microstructural control on two different length scales (in the present case, at 48 and 350 angstroms) was then used to introduce temperature-dependent transitions in electrical conductivity.
620 citations
TL;DR: The great variety of morphologies displayed by these block copolymers and the fact that they are easily accessible from poly(styrene) and different types of peptides open new opportunities for applications in the fields of life and materials sciences.
Abstract: Amphiphilic block copolymers containing a poly(styrene) tail and a charged helical poly(isocyanide) headgroup derived from isocyano-L-alanine-L-alanine and isocyano-L-alanine-L-histidine were prepared. Analogous to low-molecular mass surfactants, these block copolymers self-assembled in aqueous systems to form micelles, vesicles, and bilayer aggregates. The morphology of these aggregates can be controlled by variation of the length of the poly(isocyanide) block, the pH, and the anion-headgroup interactions. The chirality of the macromolecules results in the formation of helical superstructures that have a helical sense opposite to that of the constituent block copolymers. The great variety of morphologies displayed by these block copolymers and the fact that they are easily accessible from poly(styrene) and different types of peptides open new opportunities for applications in the fields of life and materials sciences.
548 citations
Patent•
02 Oct 1998
TL;DR: A block copolymer made of a major amount of hydrophobic poly(lactide-co-glycolide) copolymers and a minor amount of a hydrophilic polyethylene glycol polymer B-block, having an overall average molecular weight of between about 3100 and 4500, possesses reverse thermal gelation properties.
Abstract: A water soluble biodegradable ABA-type block copolymer made up of a major amount of hydrophobic poly(lactide-co-glycolide) copolymer A-blocks and a minor amount of a hydrophilic polyethylene glycol polymer B-block, having an overall average molecular weight of between about 3100 and 4500, possesses reverse thermal gelation properties. Effective concentrations of the block copolymer and a drug may be uniformly contained in an aqueous phase to form a drug delivery composition. At temperatures below the gelation temperature of the copolymer the composition is a liquid and at temperatures at or above the gelation temperature the composition is a gel or semi-solid. The gelation temperature is preferably at or below body temperature of a warm-blooded animal. The composition may be administered to a warm-blooded animal as a liquid by parenteral, ocular, topical, transdermal, vaginal, transurethral, rectal, nasal, oral, or aural delivery means and is a gel at body temperature. The composition may also be administered as a gel. The drug is released at a controlled rate from the gel which biodegrades into non-toxic products. The release rate of the drug may be adjusted by changing various parameters such as hydrophobic/hydrophilic component content, copolymer concentration, molecular weight and polydispersity of the block copolymer. Because the copolymer is amphiphilic it functions to increase the solubility and/or stability of drugs in the composition.
450 citations
TL;DR: In this article, the morphological development in solvent-cast polystyrene thin films is described as a function of solvent evaporation, and a morphological morphological model for polybutadiene (PB) is proposed.
Abstract: This paper describes morphological development in solvent-cast polystyrene (PS)−polybutadiene (PB)−polystyrene (SBS) triblock copolymer thin films (30 wt % PS) as a function of solvent evaporation ...
432 citations
TL;DR: In this article, a wide range of bilayer aggregates, among them tubules, vesicles, large compound Vesicles (LCVs), and lamellae, were prepared from various polystyrene-b-poly(ethylene oxide) (PS-b -PEO) diblock copolymers, and studied by transmission electron microscopy (TEM).
Abstract: A wide range of bilayer aggregates, among them tubules, vesicles, large compound vesicles (LCVs), and lamellae, were prepared from various polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblock copolymers, and studied by transmission electron microscopy (TEM). The preparation method involved copolymer dissolution in DMF at room temperature, followed by the addition of water. In addition, it was found that aggregates of various morphologies can be prepared from an identical block copolymer by changing the solvent from DMF to a water−DMF mixture, by the addition of electrolytes, or by the use of subambient temperatures. All of these methods can be used to facilitate the formation of specific bilayer aggregates. When the preparation method involved copolymer dissolution in water−DMF mixtures, it was found that the morphologies of aggregates under certain conditions also depended on the annealing time. For example, the ratio of tubules to vesicles is related to the annealing time; only tubules appear at long a...
430 citations
TL;DR: It was found that a dimer of adriamycin molecules formed and that this dimer was physically entrapped in the inner core of the micelle as well as intact ADR, indicating that the physicallyEntrapped ADR played a major role in antitumor activity in vivo.
424 citations
TL;DR: Optimize systems were found to form adhesive bonds that rival in strength those formed by natural marine adhesive proteins, which are readily prepared in large quantities and require no enzymes or other biological components.
Abstract: Water soluble copolypeptides containing l-dihydroxyphenylalanine (DOPA) and l-lysine were prepared by ring-opening polymerization of α-amino acid N-carboxyanhydride (NCA) monomers. We have prepared a range of different copolymers to probe the effects of functional group composition on adhesive and cross-linking behavior. Aqueous solutions of these copolymers, when mixed with a suitable oxidizing agent (e.g., O2, mushroom tyrosinase, Fe3+, H2O2, or IO4-), formed cross-linked networks that were found to form moisture-resistant adhesive bonds to a variety of substrates (e.g., aluminum, steel, glass, and plastics). It was found that successful adhesive formation was dependent on oxidation conditions, with chemical oxidants giving the best results. Optimized systems were found to form adhesive bonds that rival in strength those formed by natural marine adhesive proteins. Our synthetic systems are readily prepared in large quantities and require no enzymes or other biological components.
421 citations
TL;DR: The story of the discovery of the metallocene-methylaluminoxane catalysts for olefin polymerization is reviewed from its conception up until the first commercial production of polymers in this paper.
Abstract: The fascinating story of the discovery of the metallocene–methylaluminoxane catalysts for olefin polymerization is reviewed from its conception up until the first commercial production of polymers. A great number of different titanocenes and zirconocenes have been synthesized that give tailored polymers of totally different structures, and allows control of polymer tacticity, molecular weight and molecular weight distribution to be more efficient. New kinds of copolymers and elastomers can be synthesized.
404 citations
TL;DR: In this article, it was shown that the morphologies and other characteristics of crew-cut aggregates of polystyrene-b-poly(acrylic acid) (PSb-PAA) diblock copolymers are related to the nature of the initial common solvent in which the micelle-like aggregates are prepared.
Abstract: It is shown that the morphologies and other characteristics of crew-cut aggregates of polystyrene-b-poly(acrylic acid) (PS-b-PAA) diblock copolymers are related to the nature of the initial common solvent in which the micelle-like aggregates are prepared. Polymer−solvent interactions determine the dimensions of both the core and the corona of the aggregates. Solubility parameters and dielectric constants of the solvents can be used to estimate the strength of the PS−solvent interaction (which influences the solvent content in the core) and the strength of PAA−solvent interaction (which influences the repulsion among corona chains). The closer the match between the solubility parameter of the solvent and that of the core forming block, the higher the solvent content of the core and the higher the degree of stretching of the core chains. The lower the polarity of the solvent, the weaker the PAA−solvent interaction and the weaker the repulsive interactions among the corona chains; this increases the aggregat...
397 citations
TL;DR: The mechanical relaxation behavior and microstructure of a series of novel norbornyl−POSS organic−inorganic copolymers have been investigated in this article, where it was observed that POSS copolymerization enhances the α-relaxation temperature, Tα, in proportion to the weight fraction of the POSS−norbornyl comonomer.
Abstract: The mechanical relaxation behavior and microstructure of a series of novel norbornyl−POSS organic−inorganic copolymers have been investigated. We have examined the influence on physical properties of both the weight fraction of POSS−norbornyl monomer and the corner group composition. POSS refers to the polyhedral oligomeric silsesquioxane inorganic/organic macromer, which is composed of an inorganic Si8O12 spherical core surrounded by seven inert organic corner groups and one reactive norbornyl moiety. It was observed that POSS copolymerization enhances the α-relaxation temperature, Tα, in proportion to the weight fraction of the POSS−norbornyl comonomer. Interestingly, however, the magnitude of this dependence is larger for the POSS−norbornyl comonomer possessing cyclohexyl corner groups (CyPOSS) than for the copolymer with cyclopentyl corner groups (CpPOSS). Although POSS copolymerization yields only slight enhancement of the room temperature storage modulus, at temperatures lower than a strong mechanic...
TL;DR: The phase behavior of PEO−PEP/epoxy blends, with compositions spanning 10−93 wt % block copolymer, was investigated in the uncured state (without hardener) using small-angle X-ray scattering (SAXS) and dynamic mechanical spectroscopy.
Abstract: Thermoset materials containing ordered structures with ∼10-nm dimensions were prepared from a mixture of a low-molecular-weight poly(ethylene oxide)−poly(ethylene-alt-propylene) (PEO−PEP) diblock copolymer and a poly(Bisphenol-A-co-epichlorohydrin) epoxy resin that selectively mixes with the PEO block. The phase behavior of PEO−PEP/epoxy blends, with compositions spanning 10−93 wt % block copolymer, was investigated in the uncured state (without hardener) using small-angle X-ray scattering (SAXS) and dynamic mechanical spectroscopy. Without hardener, the phase behavior of block copolymer/epoxy blends was similar to model block copolymer/homopolymer blends and varied with changes in the blend composition and temperature. The following morphologies were observed with increasing epoxy concentration: lamellar, cubic bicontinuous, hexagonally packed cylinders, body-centered cubic packed spheres, and disordered micelles. Methylene dianiline, an aromatic amine hardener, was added to the blends, and the real-tim...
IBM1
TL;DR: In this article, a variety of high molecular weight, thermally stable, blue-light-emitting random copolymers of 9,9-di-n-hexylfluorene by nickel(0)-mediated polymerization are presented.
Abstract: We have prepared a variety of high molecular weight, thermally stable, blue-light-emitting random copolymers of 9,9-di-n-hexylfluorene by nickel(0)-mediated polymerization. The copolymers are readily soluble and easily processable from organic solvents. Both the polymer and electronic properties may be tuned by selection of comonomer structure. The electronic properties also vary with composition and film morphology. A blue-light-emitting device has been prepared using ionic salts for electrochemical doping.
Patent•
22 Jun 1998
TL;DR: The adherent coating of the invention comprises a stabilizing polymer together with an active agent (a hydrophilic polymer and/or a bioactive agent) in a layer bonded to the surface of a medical device as discussed by the authors.
Abstract: The adherent coating of the invention comprises a stabilizing polymer together with an active agent (a hydrophilic polymer and/or a bioactive agent) in a layer bonded to the surface of a medical device. This invention encompasses the coating liquids used for coating medical devices, methods of coating the devices, and the coated devices. The stabilizing polymer is selected to entrap the active agent in a coating that has a high degree of flexibility and has improved bonding to a wide variety of substrates. Preferred stabilizing polymers are cross-linkable acrylic and methacrylic polymers, ethylene acrylic acid copolymers, styrene acrylic copolymers, vinyl acetate polymers and copolymers, vinyl acetal polymers and copolymers, epoxy, melamine, other amino resins, phenolic polymers, copolymers thereof, and combinations.
TL;DR: The results indicated that the drug-loaded nanospheres could be useful as a novel drug carrier in injectable delivery systems for hydrophobic drugs.
TL;DR: In this article, the structure of thin films of a symmetric diblock copolymer, P(dS-b-MMA) (dS = perdeuterated styrene, MMA = methyl methacrylate), was investigated near preferential and nonpreferential (neutral) surfaces.
Abstract: The structure of thin films of a symmetric diblock copolymer, P(dS-b-MMA) (dS = perdeuterated styrene, MMA = methyl methacrylate), was investigated near preferential and nonpreferential (neutral) surfaces. Neutral surfaces were achieved at the substrate and air interfaces by localizing random copolymer, P(S-r-MMA), having a styrene fraction of 0.60, to each of these interfaces. This was performed by chemically grafting the random copolymer to the substrate and anchoring a surface active random copolymer having a perfluorinated end group to the air interface, respectively. Neutron reflectivity and small-angle neutron scattering were used to determine the orientation of the lamellar microdomains for films having various boundary conditions. Successive steps of CF4 reactive ion etching followed by field emission scanning electron microscopy were used to ascertain the orientation of the microdomains as a function of film depth. For films confined between two continuous neutral surfaces, the orientation of the...
TL;DR: A pronounced effect of the molecular weight of the polymer on the transfection efficiency was observed, and an increasing molecular weight resulted in an increasing number of transfected cells.
TL;DR: An AB block copolymer of oligo(methyl methacrylate) (oMMA) and poly(acrylic acid) (PAAc) has been synthesized and can be useful for prolonged mucosal drug delivery of hydrophobic drugs.
TL;DR: Physico-chemical aspects of formation and behavior of interpolyelectrolyte and block ionomers complexes are discussed and recent results on the use of block ionomer complexes for gene delivery are presented.
TL;DR: In this paper, the orientation of diblock copolymer microdomains (made up of nanoscopic cylinders, or lamellae) was controlled by anchoring random copolymers to both interfaces of the film.
Abstract: Diblock copolymers are composed of two chemically distinct chains covalently bonded together at one end. We have discovered how to control the orientation of diblock copolymer microdomains (made up of nanoscopic cylinders, or lamellae) in thin films. To do this, we eliminated all preferential interfacial segregation of the components by anchoring random copolymers, composed of identical monomers to the diblock copolymer, to both interfaces of the film. The composition of the random copolymer is tailored to balance interactions between the segments of the copolymer and the interfaces.
TL;DR: In this paper, a study of the mechanical properties and structural heterogeneity of crosslinked polymers formed by photopolymerization of multifunctional monomers is described. But the results indicate that the structural heterogeneity increases as the crosslinking density of the copolymer is increased.
TL;DR: The selected solvents used to prepare micelles by dialysis in water affect the size of polymeric micelle, and an increase of molecular weight and hydrophobic components of diblock copolymer produced larger micells.
TL;DR: The first organometallic−inorganic diblock copolymer, poly(ferrocenyldimethylsilane)-b-poly(dimethylsiloxane) (PFS-b-PDMS) (block ratio = 1.0:6.0) with a narrow molecular weight was proposed in this article.
Abstract: The novel organometallic−inorganic diblock copolymer, poly(ferrocenyldimethylsilane)-b-poly(dimethylsiloxane) (PFS-b-PDMS) (block ratio = 1.0:6.0) (Mn = 35 100 g/mol with a narrow molecular weight ...
TL;DR: The thermally sensitive block copolymer system synthesized by ring-opening polymerization of dl-lactide initiated from hydroxy-terminated poly (N-isopropylacrylamide) (PIPAAm-PLA) is interesting from both applied and fundamental perspectives, particularly for active targeting as drug carriers.
TL;DR: Micelles formed from polycaprolactone-b-poly(ethylene oxide) diblock copolymers were investigated as a novel drug delivery system and as a delivery vehicle for the neurotrophic agents FK506 and L-685,818 in PC 12 cell cultures.
TL;DR: In this article, an aqueous micellar polyacrylamides hydrophobically modified with a small amount of HMPAM was prepared by means of an annealing mousellar polymerization technique, where the hydrophobic molecules were randomly distributed as blocks in the acrylamide backbone.
TL;DR: In this paper, light scattering and pH titration were used to examine the binding of bovine serum albumin (BSA) to poly(diallyldimethylammonium chloride) (PDADMAC), poly(acrylamidomethylpropyl sulfonate) (PAMPS), polymethacryl-polygonal polyanion (PMAPTAC), and an AMPS−ACrylamide random copolymer (pAMPS80AAm20) was found to vary linearly with the square
Abstract: Light scattering and pH titration were used to examine the binding of bovine serum albumin (BSA) to poly(diallyldimethylammonium chloride) (PDADMAC), poly(acrylamidomethylpropyl sulfonate) (PAMPS), poly(methacrylamidopropyltrimethylammonium chloride) (PMAPTAC), and an AMPS−acrylamide random copolymer (PAMPS80AAm20). The critical protein charge required to induce protein−polyelectrolyte complexation, (Zpr)c, was found to vary linearly with the square root of the ionic strength (I1/2), i.e., with the Debye−Huckel parameter (κ), the proportionality constant being a function of polyelectrolyte chain parameters such as intrinsic stiffness and charge density. This linearity was remarkably continuous through Zpr = 0, with (Zpr)c occurring predominantly “on the wrong side” of the isoionic point; i.e., the onset of binding was typically observed when the global protein charge was of the same sign as the polyelectrolyte. Binding of BSA to the lower charge density polyanion (PAMPS80AAm20) unexpectedly occurred under...
TL;DR: In this paper, the effects of block composition on the self-assembly and resulting microstructure of amphiphilic block copolymers in the presence of selective solvents (water and oil) were examined.
Abstract: The study addresses the effects of block composition on the self-assembly (and resulting microstructure) of amphiphilic block copolymers in the presence of selective solvents (“water” and “oil”) by examining the ternary phase behavior and structure of two copolymers, E20P70E20 and E100P70E100, having the same block architecture (ExPyEx) and P:poly(propylene oxide) middle-block size but different E:poly(ethylene oxide) end-block sizes (Pluronic P123, E20P70E20, contains 30% E and Pluronic F127, E100P70E100, 70% E). A characterization (using SAXS and deuterium NMR) of the ternary isothermal (25 °C) E20P70E20−butyl acetate−water and E20P70E20−butanol−water systems is presented first. A variety of lyotropic liquid-crystalline (LLC) phases are thermodynamically stable in the former (butyl acetate) system, both of the “normal” (oil-in-water) and of the “reverse” (water-in-oil) morphology. In the latter (butanol) system, the reverse LLC phases are not stable but are replaced by an extensive water-lean solution r...
TL;DR: In this article, the LP-ARTICLE-1998-001 was updated with a 3.0.2-Y Record created on 2005-07-07, modified on 2017-05-10.
Abstract: Reference LP-ARTICLE-1998-001doi:10.1002/(SICI)1521-4095(199801)10:2 3.0.CO;2-Y Record created on 2005-07-07, modified on 2017-05-10
TL;DR: In this paper, X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that so-modified silicate layers were finely dispersed in these polymeric matrices.
Abstract: Nanoscale composites of a modified silicate with either high-density polyethylene (HDPE) or a nitrile copolymer have been examined. Hydrophilic silicate clay was intercalated by ion exchange reaction of alkylammonium ions. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that so-modified silicate layers were finely dispersed in these polymeric matrices. Instead of being individually dispersed, most layers were found in thin stacks comprising several swollen layers. Greater dispersion was found in the nitrile copolymer rather than in HDPE, suggesting differences in the degree of physical interaction with the modified clay. Lamellar crystals of HDPE formed parallel to the silicate layers.