Backbone Of Poly Research Articles

Synthesis of Poly(tetrahydrofuran) Polymacromonomers Having Mixed Branch Segments through Reshuffling in Electrostatic Self-Assembly and Subsequent Covalent Fixation

A new polymacromonomer architecture with mixed branch segments of different lengths has been constructed through reshuffling of poly(tetrahydrofuran), poly(THF), segments in an electrostatic self-assembly and subsequent covalent fixation process. Thus, two types of electrostatically self-assembled polymacromonomer precursors 4a and 4b were prepared by the ion-exchange reaction between α-methoxy-ω-(N-phenylpyrrolidinium) poly(THF)s (1a and 1b) (Mn = 3000 and 6200, respectively) and a poly(sodium acrylate) (DP = 52), respectively. By reshuffling of different poly(THF) segments in the two polymer precursors, 4a and 4b, a new electrostatically self-assembled precursor, 4[a,b], was obtained. The subsequent heat treatment of 4[a,b] effectively produced a covalently linked polymacromonomer, 5[a,b], having mixed branch segments through the ring-opening reaction of the pyrrolidinium salt groups in 1a and in 1b by carboxylate anions in the backbone poly(acrylate) component.

Uranyl ion complexation of 2,2′‐dihydroxyazobenzene enhanced on a backbone of poly(ethylenimine)

Uranyl ion complexation of 2,2′‐dihydroxyazobenzene enhanced on a backbone of poly(ethylenimine)

Conjugated copolymers of 2-methoxy-5-2′-ethyl-hexyloxy-1,4-phenylenevinylene and 2,5-dicyano-1,4-phenylenevinylene as materials for polymer light-emitting diodes

A new series of electroluminescent polymers has been synthesized by incorporating the segments of 2,5-dicyano-1,4-phenylenevinylene (DCN-PV) into the backbone of poly(2-methoxy-5-(2′-ethyl-hexyloxy)- p-phenylene vinylene) (MEH-PPV). The copolymers have similar optical properties with MEH-PPV. The oxidation potentials of the copolymers are slightly larger than that of MEH-PPV. The copolymers exhibit “pre-reduction” processes, beginning at about −0.9 V (vs. SCE), before the main reduction processes. The “pre-reduction” feature is thought to be helpful in improving electron injection, and thus to be helpful in improving EL performance. The improved EL performance of the copolymers in comparison with MEH-PPV is demonstrated by a single-layer polymer light-emitting diode (PLED) device employing one of the copolymers as the emissive material.

Carrier design: new generation of polycationic branched polypeptides containing OH groups with prolonged blood survival and diminished in vitro cytotoxicity.

For the construction of macromolecule-drug conjugates, it is important to provide rational basis to the selection of proper carrier. With respect to the importance of the side-chain structure and charge of the branched polypeptides in biological properties, we have prepared a new class of branched polypeptides with single or multiple hydroxyl groups and studied their solution conformation, in vitro cytotoxicity, biodistribution, and immunoreactivity. For comparative studies, polypeptides were designed to contain serine at various positions of the side chains, varying also the number. Ser was attached to the end of oligo(DL-Ala) side chains grafted to polylysine resulting polypeptides with the general formula poly[Lys(Ser(i)-DL-Ala(m))], (SAK). Ser was also coupled directly to the polylysine backbone poly[Lys(Ser(i))] (S(i)K) and then elongated by polymerization of N-carboxy-DL-Ala anhydride resulting poly[Lys(DL-Ala(m)-Ser(i))] (ASK). An additional polymer was also prepared, but instead of the oligo(DL-Ala) branches, oligo(DL-Ser) side chains were introduced (poly[Lys(DL-Ser(m))], SK). The presence of hydroxyl groups resulted in compounds with improved of water solubility. CD spectra of polypeptides showed significant differences correlating with the position and numbers of Ser residues in the side chains. Under physiological conditions, polycationic polypeptides assumed ordered secondary structure (S(i)K and LSK) or partially unordered conformation (SK, SAK, and ASK). Data of selected polymers demonstrate that these polycationic compounds are essentially nontoxic in vitro on normal rat liver or mouse spleen cells and have no cytostatic effect on mouse colorectal carcinoma C26 cells. The blood clearance and biodistribution of these derivatives were greatly dependent on the position and number of Ser residues in the branches and possess a rather extended blood survival in mice. Polypeptides were taken up predominantly by the liver and kidney (S(i)K, LSK, and ASK) or kidney and lung (SK and SAK). The best survival in the blood was found with SAK, representing the first polycationic branched polypeptide, which show extended blood clearance. The relative position of Ser residue had also a marked influence on the immunogenicity of polypeptides. The characteristics of the antibody response to polypeptide containing Ser at the end of the branches (SAK) or adjacent to the polylysine backbone (ASK) was also dependent on the genetic background of the mouse strains. We also found that these compounds have no effect on to the SRBC-specific humoral immune response, indicating the lack of nonspecific immunostimulatory potential. In conclusion, these studies suggest that synthetic branched polypeptides with Ser can be considered as candidates for constructing suitable conjugates for drug/epitope delivery. It is not only due to the presence of hydroxyl group to be used for oxime chemistry but also to their beneficial biological features.

Organic Artificial Proteinase with Active Site Comprising Three Salicylate Residues

The first organic artificial proteinase based on synthetic materials is obtained by building active sites on the backbone of poly(ethylenimine) (PEI). The active site comprising three salicylate residues is prepared by preassemblage of three molecules of a salicylate derivative with Fe(III) ion followed by cross-linkage of the salicylates with PEI and demetalation of the resulting polymer. Proteinase activity of the artificial enzyme is demonstrated with hydrolytic cleavage of γ-globulin (Gbn). Both the heavy (50 kDa) and the light (25 kDa) chains of Gbn are effectively cleaved into peptides smaller than 5 kDa. The optimum activity of the artificial proteinase is manifested at pH 5−7. The half-life for cleavage of the two chains of Gbn by the artificial proteinase is ∼1 h at pH 7 and 50 °C when the concentration of the artificial active site is 0.4−1 mM. The activity (at pH 7) of the artificial proteinase prepared with PEI is comparable to that (at pH 9) of a catalytic antibody elicited by a joint hybridoma and combinatorial antibody library approach and to that (at pH < 3) achieved by the intramolecular carboxyl group in the hydrolysis of N-methyl maleamic acid. Thus, the approach reported here is useful for designing active sites of artificial enzymes.

Spectroelectrochemistry of Electrogenerated Tetrathiafulvalene-Derivatized Poly(thiophenes): Toward a Rational Design of Organic Conductors with Mixed Conduction

Thin films of tetrathiafulvalene (TTF) derivatized polythiophenes were prepared by electropolymerization of precursors based on bithiophene or hybrid thiophene−ethylenedioxythiophene (EDOT). The cyclic voltammogram of these polymers exhibits an additional anodic wave between the two oxidation steps corresponding to the formation of the TTF cation radical and dication. The electrochemically induced spectral changes associated with these various oxidation processes were analyzed on equilibrated films and in dynamic conditions using classical and time-resolved spectroelectrochemical techniques. In spite of a complex behavior due to the overlap of the various TTF oxidations with the doping process of the π-conjugated supporting PT backbone, the different monomeric and dimeric oxidized TTF species present in the polymers were unequivocally identified. Comparison of the two polymers shows that whereas for poly(1) oxidation of TTF precedes the PT doping, the presence of EDOT in the PT backbone of poly(2) leads to the reverse situation. On the basis of these results, the structural conditions required to develop a novel class of organic conductors with mixed conduction are discussed.

Adsorption behaviour of amphiphilic polymers at hydrophobic surfaces: effects on protein adsorption

The adsorption of four different amphiphilic polymers to a model surface has been studied, and the effects of the adsorbed amphiphiles on the subsequent adsorption of fibrinogen (Fg) and human serum albumin (HSA) at the surfaces were investigated. The amphiphilic polymers were one commercially available ABA block copolymer, Pluronic PE9400 (PE94), composed of poly(ethylene oxide) (A-blocks) and poly(propylene oxide) (B-block), and three graft copolymers, two with backbones of poly(styrene-co-acrylamide) (STY) and one with a backbone of poly(methyl methacrylate-co-ethylhexyl methacrylate) (ACRY). The backbones carried poly(ethylene oxide) (PEO) grafts. The model surface was a hydrophobic methylated silica surface (HMS). The amphiphilic polymers were adsorbed at the HMS surface from an ethanol/water solution. The adsorption process was monitored by ellipsometry. After rinsing with phosphate buffered saline (PBS), protein was added and the continued adsorption measured by ellipsometry. Surfaces modified by adsorption of the amphiphilic polymers were also characterized by contact angle measurements and X-ray photoelectron spectroscopy (XPS). According to these measurements the amphiphilic polymers adsorbed in significant amounts at the HMS surface. A limited study by atomic force microscopy (AFM), as well as the XPS measurements, suggests that both single molecules and micellar aggregates adsorb at the surface. ACRY and PE94 gave the highest levels of adsorption. As compared to the Pluronic block copolymer the graft copolymers were more strongly attached to the HMS surface, as shown by less desorption on rinsing with solvent. The ellipsometric results show that the adsorption of HSA and Fg at HMS surfaces containing preadsorbed amphiphilic polymer was significantly reduced as compared to the bare HMS surface. ACRY and PE94 showed the largest effects. Both polymers gave more than a 20-fold reduction of the Fg adsorption and a 10-fold reduction of the HSA adsorption. The STY polymers reduced the protein adsorption by a factor of 2-3.

ChemInform Abstract: Models of Biopolymers and Bioanalogous Polymers with Backbones of Poly( alkylene phosphate)s

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Graft copolymers as stabilizers for oil-in-water emulsions Part 2. Preparation of the emulsions and the factors affecting their stability

Oil-in-water emulsions were prepared using a series of synthetic graft copolymers with a backbone of poly(methyl methacrylate) and a number of side-chains of poly(ethylene glycol). The properties of such preparations are reported in a separate paper (Part 1 of this communication; A.E. Cárdenas-Valera, A.I. Bailey and A. Doroszkowski, Colloids Surfaces A: Physicochem. Eng. Aspects 96(1995)53–57). The organic phase was toluene, n-heptane or a mixture of the two materials. The emulsions were characterized for mean droplet diameter by means of a laser scattering technique. The stability of the emulsions was monitored as a function of time by the observation of changes in the mean droplet size distribution. Drainage tests were also carried out. The results were correlated with the structure of the molecules, their conformation at the interface, and formulation variables such as the water/oil ratio and surfactant concentration. The results show that stability is enhanced by increasing the thickness and density of the sheath formed around the oil droplet. For copolymers containing a large proportion of the stabilizing moiety (>40%), the addition of heptane to the organic phase leads to a more stable emulsion. This is due to the reduction of the solvency of the backbone in the oil phase which pushes it towards the plane of the interface, thus achieving better interfacial coverage.

Graft copolymers as stabilizers for oil-in-water emulsions Part 1. Synthesis of the copolymers and their behaviour as monolayers spread at the air-water and oil-water interfaces

A series of graft (comb) copolymers having a range of emulsifying properties has been prepared. Each molecule has a backbone of poly(methyl methacrylate) (PMMA) and a number of side-chains of methoxy-poly(ethylene oxide) (MeOPEG). The intermediate PEG methacrylate was synthesized by the ester interchange method. The copolymerization was carried out by means of the free radical method. The molecules were prepared having different number. length and spacing of the PEG side-chains and their overall molecular weight was varied between 7000 and 20 000. The variation of surface interfacial pressure, π, with compression of spread monofilms of these copolymers was studied. For the interfacial studies the influence of the solvency conditions of the anchor (PMMA) on the π A curves and on the resulting conformational changes occuring at such interfaces was also investigated.

Synthesis and characterization of novel toughened thermosets derived from pendent amines on the backbone of poly(arylene ether sulphone)s

Random incorporation of pendent aryl amines on the backbone of poly(arylene ether sulphone)s was achieved by the copolymerization of a minor amount of a second activated aromatic dihalide, bis(4-fluorophenyl)-3-aminophenylphosphine oxide (amino DFTPPO), with 4,4′-dichlorodiphenylsulphone (DCDPS) and bisphenol A via aromatic nucleophilic substitution polymerization using N-methylpyrrolidone (NMP) as the solvent, toluene as the azeotroping agent and potassium carbonate as the base. The pendent amines were optionally chemically modified by conversion to maleimides and thermally cured to afford tough insoluble networks. Epoxy networks were also obtained by reacting the pendent amines with liquid epoxy resin and 4,4′-diaminodiphenylsulphone (DDS). The synthesis and characterization of these novel thermosetting materials were investigated, and it was demonstrated that selected compositions could significantly improve the fracture toughness of the epoxy networks. Two important variables identified were the weight or volume fraction of the thermoplastic modifier and, importantly, the concentration of the pendent aminophenyl ‘cure’ sites. In this research, about 2.5 mol% cure sites was the optimum concentration utilized, which produced tough multiphase systems. Higher aminophenyl concentrations resulted in more homogeneous morphologies and fracture toughness was about the same as the control.

Synthesis and flammability of copolyisophthalamides. I. With phosphorus groups in the main chain

AbstractThe influence of certain phosphorus substituted (OH, OMe, Me) 3,3'‐diphenylphosphine oxides on flammability and thermal stability of 1,3‐phenylene isophthalamide copolymers was investigated. Introduction of the above phosphorus groups along the backbone of poly(1,3‐phenylene isophthalamide) was performed in a random manner to a degree of ca. 5‐15 mol %. From the limiting oxygen index (LOI) measurements on copolymers, it was found that the diphenylphosphinic acid group has the highest flame retardance efficiency with an increase of LOI 44‐56%. From thermogravimetric analysis (TGA), it was found that the action of phosphorus groups is limited in the solid phase, increasing the char yield to 27‐42%. This was attributed to crosslinking reactions at the stage of amide bond decomposition. © 1992 John Wiley &amp; Sons, Inc.

Temperature Dependence of PHB Hole Profiles in Polymer Matrices

The temperature dependences of irreversible hole decay for tetraphenylporphines / polymers as guest / host systems were investigated. The irreversible hole decay values depend on the chemical structure of matrix polymers. Irreversible hole decay is caused by the motion of polymer side chains or backbones of poly(alkyl methacrylate)s and polyethylene. Excellent hole retention is observed in the PMMA matrix, and is explained by the small, symmetrical structure of methyl groups. PnDMA shows hole decay profiles similar to those of PE. This result indicates that PnDMA forms microstructures that are similar to PE microstructures because of long methylene side chains.

Use of phosphorothioate analogs of poly(dA-dT) · poly(dAdT) to study steroidal-diamine induced conformational change in poly(dA-dT) · poly(dA-dT)

Introduction of phosphorothioate groups into the backbone of poly(dA-dT) allows one to label the d(ApT) and d(TpA) phosphate resonances in the 31P NMR spectrum. Upon binding the steroidal diamine dipyrandenium to poly d(AsT) and poly d(TsA), 31P NMR shows that it is the d(ApT) phosphodiester bond which is most perturbed. Other work has shown that 2 M Cs + causes the same 31P shift. The DNA conformational change induced by both cations probably involves a narrowing of the minor groove. 31P NMR DNA phosphorothioate Steroidal diamine DNA conformation

Surface modification of polymethyl methacrylate by graft copolymers

Graft copolymers composed of poly(methyl methacrylate) branches and different backbones of poly(fluoroalkyl acrylate(FA)-co-methyl methacrylate(MMA)), poly (hydroxyethyl methacrylate(HEMA)-co-MMA), and poly(FA-co-HEMA) were prepared by macromonomer technique to study their application as a surface modifier for PMMA films. Contact angle of water droplet on PMMA film specimens containing various amounts of these graft copolymers cast on glass slides from THF solution was found to change considerably with the graft copolymer concentration, depending on their backbone component. And there was considerable difference in contact angle between air and glass side of the film surfaces. These results were considered in terms of the surface accumulation of graft copolymers during the solvent evaporation.

Effect of graft copolymer on demixing of immiscible polymers in solution

AbstractThe effect of graft copolymer on the demixing of solutions of two immiscible homopolymers and critical conditions for emulsion formation were studied. The graft copolymer used in the present work consists of one backbone poly(vinyl acetate) (PVAc) and one branch polystyrene (PS). PVAc and PS of various degrees of polymerization were used as immiscible homopolymers. The common solvent was benzene. When the concentration of homopolymer blend was not sufficiently higher than the critical concentration for demixing of the blend solution, no stable emulsion was formed, even when a considerable amount of graft copolymer was present, and the added graft copolymer merely reduced the demixing rate. However, as the blend concentration was increased, a stable emulsion could readily be obtained by addition of rather small amounts of graft copolymer. The radius of emulsion droplets was inversely proportional to the weight ratio of the graft copolymer to the dispersed component polymer, in accordance with the theoretical prediction. It was concluded that the emulsions were stabilized against coagulation by graft copolymer molecules fixed strongly as a monolayer on the interface of the emulsion.

Thermally stable silarylene‐1,3,4‐oxadiazole polymers

AbstractThe effects of incorporating a p‐phenylene‐ (or m‐phenylene)‐1,3,4‐oxadiazole fragment into the backbone of poly[1,4‐phenylene(diphenylsilyl)‐1,4‐phenylene‐2,5‐(1,3,4‐oxadiazole)], which was developed by the authors, was investigated. Bis[(p‐carbohydrazidophenyl)]diphenylsilane was copolymerized with dipentachlorophenyl terephthalate or isophthalate to produce the prepolymers poly[N‐(p‐diphenylsilylbenzoyl)‐N′N″‐(terephthaloyl)‐N″′‐(p‐benzoyl)dihydrazide] and poly[N‐(p‐diphenylsilylbenzoyl)‐N′,‐N″‐(isophthaloyl)‐N″′‐p‐(benzoyl) dihydrazide], respectively. The polyhydrazides were converted by thermal dehydration into poly[1,4‐phenylene(diphenylsilyl)‐1,4‐phenylene‐(1,3,4‐oxadiazole‐2,5‐diyl)‐1,4‐phenylene‐2,5‐(1,3,4‐oxadiazole)] and poly[1,4‐phenyl‐ene(diphenylsilyl)‐1,4‐phenylene‐(1,3,4‐oxadiazole‐2,5‐diyl)‐1,3,4‐(oxadiazole)]. The new polymers were soluble in organic solvents. Films cast from these solutions exhibited good adhesion to glass and metal surfaces. Thermal analysis showed that the heat stability of all these polymers was about the same and that they were resistant to decomposition when heated in air to about 400°C. The results also indicated that these polymers were somewhat less heat‐resistant than samples of poly‐[1,4‐phenylene(diphenylsilyl)‐1,4‐phenylene‐2,5‐]1,3,4‐(oxadiazole) synthesized from bis(p‐carbohydrazidophenyl)diphenylsilane and bis‐(p‐carbopentachlorophenoxy‐phenyl)diphenylsilane.