Block copolymers with poly(oxy-1,4-phenylene) and liquidcrystalline polyester segments

Block copolymers were synthesized composed of an isotropic, crystallizable poly(oxy-1,4-phenylene) block and a thermotropic liquid-crystalline (LC) polyester block. Crystalline as well as amorphous LC polyesters were used, derived from substituted poly(1,4-phenylene terephthalate). The block of poly(oxy-1,4-phenylene) was introduced via telechelic 1 . 1 was prepared with a functionality of 2 in a Cu-catalyzed reaction of 4-bromophenolate 4 with 4,4′-isopropylidenediphenol (bisphenol A). The molecular weight of the telechelic is given by the ratio 4 /bisphenol A. The increase in molecular weight during formation of the block copolymer is shown by viscosity and gel-permeation chromatography measurements. The maximum weight loss of the block copolymer as obtained by thermogravimetry is in the range of 450–500°C. Both segments in the block copolymers have a strong influence on their mutual crystallization behaviour. Short segments of poly(oxy-1,4-phenylene) suppress the crystallization of both blocks. When using longer segments of poly(oxy-1,4-phenylene) the melting endotherms of both blocks are observed, but the degree of crystallinity is lower than that of the homopolymers. The fracture behaviour of the liquid-crystalline polyester 2a is changed by modification with 20 wt.-% of poly(oxy-1,4-phenylene) and the shear-banded texture is lost.     

Synthesis and properties of novel block copolymers containing poly(lactic-glycolic acid) and poly(ethyleneglycol) segments

A synthetic process for obtaining high-molecular-weight block copolymers containing poly(lacticglycolic acid) and poly(ethylene glycol) segments has been established. This process involves the reaction of poly(ethylene glycols) with phosgene, followed by polycondensation of the resulting ,ω-bis (chloroformates) with poly(lactic-glycolic acid) oligomers. The copolymers have been characterized for their molecular weight, solubility properties, water absorption and preliminarily thermal behaviour. All evidence points to the conclusion that the process described is a general one, enabling biodegradable polymers to be obtained tailor-made according to specific requirements.     

Functional polymers and sequential copolymers by phase transfer catalysis, 20. Synthesis of copolymers and alternating block copolymers containing thermotropic liquid crystalline polyethers and aromatic poly(ether sulfone) segments

Copolymers and alternating block copolymers were prepared both containing a liquid crystalline (LC) polyether segment, based on 4,4′-biphenyldiol (3) and 1,5-dibromopentane (2) , and a thermoplastic segment, deriving from an aromatic poly(ether sulfone) (PSU) (1) . The alternating block copolymer was prepared by the phase transfer catalyzed (PTC) polyetherification of mesogenic α,ω-bis(5-bromopentoxy)polyether (5) with α,ω-bis(hydroxyphenyl)PSU (1) . Copolymers containing mesogenic segments were prepared utilizing α,ω-bis(hydroxyphenyl)-PSU as another diphenol in the PTC polyetherification of 5 with 2 and 3 . The thermal behavior, as characterized by differential scanning calorimetry (DSC), revealed phase separation for all prepared copolymers as well as liquid crystalline behavior down to a content of mesogenic units deriving from 5 as low as 30 wt.-%. Optical polarization microscopy, however, revealed significant differences in textures of the copolymers with the textures observed for homopolymer 5 . Textures of a 5 /PSU blend clearly show phase separation.     

Heparinizable graft copolymers from chlorosulphonated polyethylene with poly(amido-amine) segments

The synthesis and the physical characterization of three graft copolymers (PES/PAA) obtained from chlorosulphonated polyethylene (PECS) and three different secondary amino end-capped poly(amido-amine)s are reported. The properties of these heparinizable materials appear to be suitable for constructing prosthetic devices for biomedical use. The heparin adsorbing ability and the stability of the complex with heparin of the three copolymers have been evaluated, by means of biological tests, as activated Partial Thromboplastin Time (PTT) and Thrombin Time (TT).     

Synthesis and characterization of poly(ethylene oxide) and poly(perfluorohexylethyl methacrylate) containing triblock copolymers

A new series of poly(perfluorohexylethyl methacrylate)‐block‐poly(ethylene oxide)‐block‐poly(perfluorohexylethyl methacrylate), PFMA‐b‐PEO‐b‐PFMA triblock copolymers has been synthesized by atom transfer radical polymerization using bifunctional PEO macroinitiators. The molecular structure of the block copolymers was confirmed by ¹H NMR spectroscopy and SEC. X‐ray scattering studies have been carried out to investigate their bulk properties. SAXS has shown cubic arrangement of spheres (bcc), hexagonally packed cylinders (hpc) and lamellar microdomain formation in the melt of triblock copolymers investigated, depending on composition. Crystallization was, however, found to destroy the ordered melt morphology and imposes a lamellar crystalline structure. WAXS, DSC and polarized light microscopy measurements confirmed the crystallization of PEO segments in block copolymers. Long PFMA blocks were found to have significant effect on PEO crystallization.

Synthesis of triblock copolymers of EO and FMA by ATRP.     

Synthesis of a new antithrombogenic block copolymer containing fluorinated segments: poly(nonafluorohexyl acrylate-b-styrene)

Two types of block copolymers, 3a and 3b , were synthesized from α-hydro-ω-(2-hydroxyethylthio)poly[1-(3,3,4,4,5,5,6,6,6-nonafluorohexyloxycarbonyl)ethylene] ( 1a ) or α-hydro-ω-(2-aminoethylthio)poly[1-(hexyloxycarbonyl)ethylene] ( 1b ) and α,ω-bis(4-cyanatophenylthio)-poly(1-phenylethylene) ( 2 ), respectively, and the adhesion of blood platelets to these polymer surfaces was evaluated. Adhesion and activation of platelets were found to be effectively suppressed at the lamellar-microdomain surface of block copolymer 3a , having a surface free energy gap between microdomains of about 20 dyn/cm, whereas no such a suppression was observed for the microdomain structured surface of block copolymer 3b with a small surface free energy gap between the microdomains. Further, a random copolymer from nonafluorohexyl acrylate and styrene without microdomain structure does not suppress the adhesion and activation of platelets. From these results, it was concluded that the microdomain morphology and the surface free energy gap between microdomain is important to produce antithrombogenicity.     

Block copolymers of poly(ether-ether-sulfones) with liquid-crystalline/non-liquid-crystalline polyesters

The synthesis of telechellcs of poly(ether-ether-sulfones) (PEES) is controlled by high-resolution gel-permeation chromatography to optimize for low content of side products. Under optimum conditions the bifunctional polymer-homologous series is formed to 99,9%. These telechrcs were used to synthesize block copolymers with aromatic polyesters. The polyesters (PE) contain phenylhdroquinone and terephthalic acid (semicrystalline liquid-crystalline (LC) polyester), phenylterephthalic acid (amorphous LC polyester) or isophthalic acid (amorphous non-LC polyester). Block copolymers with amorphous polyesters show one glass transition temperature depending on the composition but blends of corresponding homopolymers are biphase. Block copolymers with semicrystalline LC polyesters are phase-separated. Incorporation of semicrystalline LC polyester segments into PEES increases their solvent resistance. The storage modulus of the block copolymer with 50 wt.-% of the semicrystalline polyester shows the same temperature dependence as PEES. Homogeneous block copolymers show anisotropy only if the weight fraction of polyester is larger than 0,5 whereas phase-separated systems show anisotropy at smaller fractions of polyester.     

Synthesis and characterization of ABA-triblock copolymers with polystyrene and main-chain liquid crystalline polyester segments

This paper reports on the synthesis and characterization of polystyrene-block-poly(2,2′-dimethyl-4,4′-biphenylene phenylterephthalate)-block-polystyrene. The ABA-triblock copolymers were synthesized by condensation reactions of telechelic poly(2,2′-dimethyl-4,4′-biphenylene phenylterephthalate) with anionically prepared ω-hydroxy polystyrenes. Three different lengths of the liquid-crystalline polyester (M?_n = 2650, 5 500, 10 100 g/mol) were used as central block B. The number-average molecular weight M?_n of the polystyrene segments was varied in the range of 690 to 10 000 g/mol. The liquid crystalline behavior and the transition temperatures are discussed with respect to the molecular weight of the polystyrene segments and the block copolymer composition. A comparison with the corresponding polymer blends is given and first results on the morphology of the block copolymers are presented.     

Poly(dimethylsiloxane)-poly(ethylene oxide)-heparin block copolymers. I. Synthesis and characterization

Amphiphilic block copolymers containing poly(dimethylsiloxane), poly(ethylene oxide), and heparin (PDMS-PEO-Hep) have been prepared via a series of coupling reactions using functionalized prepolymers, diisocyanates, and derivatized heparins. All intermediate steps of the synthesis yield quantifiable products with reactive end-groups, while the final products demonstrate bioactive, covalently bound heparin moieties. Due to the solvent systems required, commercial sodium heparin was converted to its benzyltrimethyl ammonium salt to enhance its solubility. The same procedure was applied to heparin degraded by nitrous acid in order to covalently couple it in solutions with the semitelechelic copolymers. As might be expected, this derivatization reduces the apparent bioactivity of the heparin. However, preliminary findings suggest that the bioactivity can be restored by reforming the heparin sodium salt.     

Synthesis and characterization of block copolymers containing cationic blocks

Poly(ethylene glycol)-poly(diallyldimethylammonium chloride) block copolymers containing nearly equal number of both monomer units were synthesized by free radical polymerization using macroazoinitiators of different molecular weights obtained from 2,2'-azoisobutyronitrile (AIBN) and poly(ethylene glycol). Characterization by elemental analysis, gel permeation chromatography and ultracentrifugation proved the formation of ABA-block copolymers. Furthermore, the polymers were characterized by DSC and viscosimetric measurements. The block copolymers lowered the surface tension of their aqueous solutions. Cross-sectional areas A_min of some of the polymers were calculated from surface tension vs. concentration isotherms. The results indicate the PEG-blocks to be adsorbed at the air-water interface, whereas the poly-(DADMAC)-block is completely present in the aqueous phase. The block copolymers are powerful stabilizers in emulsion polymerization of styrene, resulting in monodisperse cationic latexes.     

Synthesis of water-soluble biologically active phenol (or catechol) containing copolymers of N-vinyl-2-pyrrolidone

Water-soluble N-vinyl-2-pyrrolidone (VP) copolymers containing phenol (or catechol) groups in the side chains were synthesized by reactions of copolymers of VP and crotonic acid (CA) with p-aminophenol and by reaction of p-nitrophenyl ester groups containing VP-CA copolymers with dopamine. It was established that phenol (or catechol) containing multiunit VP copolymers (which were characterized by GPC, viscometry, UV, IR and ¹H NMR spectroscopy) exhibit immunostimulating activity. In addition, the phenol-containing copolymers exhibit antitumor activity. The VP-CA-p-crotonoylaminophenol terpolymer can be used as a macromolecular carrier in the synthesis of a carcinogen-polymer antigen: a polymeric azo derivative of ß-naphthylamine.     

Synthesis and electroluminescent properties of quaterphenyl and sexiphenyl containing copolymers

Copolymers containing quaterphenyl and sexiphenyl units in which the solubility was introduced by spacer groups were prepared and investigated. Photoluminescence of the compounds appears in the blue region of the visible light. Blue light emitting electroluminescent devices based on the blends of the quaterphenyl copolymer and poly(N-vinylcarbazole) with indium-tin oxide(ITO) and aluminium as hole- and electron-injecting electrodes, respectively, were fabricated. Further, the quaterphenyl copolymer was found to be nematic between 236 and 244°C.     

Biorecognition of sugar containing N-(2-hydroxypropyl)methacrylamide copolymers by immobilized lectin

The interactions of sugar containing N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers with Tetragonolobus purpureas (Lotus tetragonolobus) lectin immobilized on 4% beaded agarose have been studied. HPMA copolymers containing side-chains terminating in N-acylated amino sugars, namely, fucosylamine, galactosamine, glucosamine and mannosamine were synthesized and their biorecognition evaluated. As expected, only fucosylamine containing HPMA copolymers showed specific binding to the lectin. The dissociation constants (K_d) for HPMA copolymers were determined by frontal affinity chromatography. The binding constant was dependent on the amount of fucosylamine residues per macromolecule. An increase in fucosylamine content from 9,9 to 33,2 mol-% resulted in a decrease of K_d by one order of magnitude. Incorporation of hydrophobic side-chains such as glycylglycyl-5-[4-(2-aminoethylcarbamoyl)phenylazo]salicylic acid, 1′-(β-hydroxyethyl)-3′,3′-dimethyl-6-nitrospiro(2H-1-benzopyran-2,2′-indoline) (SP), or 1′-(β-glycylglycyloxyethyl)-3′,3′-dimethyl-6-nitrospiro(2H-1-benzopyran-2,2′-indoline) (GG-SP) into the copolymers increased the non-specific binding to the lectin. Photoinduced isomerization of bound spiropyrans to merocyanines was accompanied by changes in the conformation and biorecognition of HPMA copolymers. The results obtained demonstrated the impact of the structure and solution conformation of sugar containing HPMA copolymers on their biorecognition.     

Block copolymers by sequential group transfer polymerization: poly(methyl methacrylate)-block-poly(2-ethylhexyl acrylate) and poly(methyl methacrylate)-block-poly(tert-butyl acrylate)

Poly(methyl methacrylate)-block-poly(2-ethylhexyl acrylate) (PMMA-block-PEHA) and poly(methyl methacrylate)-block-poly(tert-butyl acrylate) with a methacrylate/acrylate unit ratio of 1:1 and 1:3, 16000 < M _n < 44000 and 1,9 < M _w/M _n < 2,5, were prepared by sequential group transfer polymerization using (1-methoxy-2-methyl-1-propenyloxy)trimethylsilane as initiator and tetrabutylammonium fluoride monohydrate as a catalyst in tetrahydrofuran at ?30°C, PMMA being the first block. The increase in M _n during the successive addition of monomers is linearly dependent on the (co)polymer yield and size-exclusion chromatography (SEC) curves are shifted towards higher molecular weights in comparison with PMMA macroinitiators. The block structure of the copolymers was also proven by extraction experiments. The presence of homopolymers in the copolymers was not detected. When the former copolymer is prepared in a reverse way (PEHA segment being the first), the MMA polymerization ceases at ≈ 43–45% conversion.     

Synthesis of N-(2-hydroxypropyl)methacrylamide copolymers with antimicrobial activity

Copolymers of N-(2-hydroxypropyl)methacrylamide which contained up to 20 mol % of p-nitrophenyl esters of N-methacryloylated oligopeptides, and of N-methacryloylaminophenoxyacetic acids (o-, m-, p-) have been prepared. The aminolyses of these polymers with tert. butylamine, ampicillin and 6-aminopenicillanic acid were kinetically characterized. Based on these results polymer bound ampicillin and polymer bound 6-aminopenicillanic acid were prepared. These preparations possessed antimicrobial activity; they inhibited the growth of Staphylococcus aureus 209 P.     

Synthesis and characterization of injectable,water-soluble copolymers of tertiary amine methacrylates and poly(ethylene glycol) containing methacrylates

Several homopolymers and copolymers of 2-(diethylamino)ethyl methacrylate (DEAEM) and poly(ethylene glycol) methyl ether methacrylate (PEGMEM) were synthesized using anionic polymerization initiated by potassium t-butoxide. The polymers were characterized by average molecular weight, polydispersity and monomeric unit composition. A very narrow molecular weight distribution was achieved with a well-controlled composition. The glass transition temperatures and compositions of the copolymers followed a Gordon-Taylor relationship. The water solubility and biocompatibility of the copolymers was compared to their parent homopolymers to determine if the addition of a poly(ethylene glycol) group was sufficient to solubilize the polymers in aqueous buffer solutions and to increase the biocompatibility of the polymers. These water-soluble, injectable cationic copolymers have potential applications in gene delivery as well as other biomaterial applications.     

Synthesis of poly(N-tert-butylaziridine) macromonomers and graft copolymers with uniform side chains

Poly(N-tert-butylaziridine) (polyTBA) macromonomers with allylamino-, allyloxy- and methacrylate end-groups were synthesized via deactivation of living polyTBA with appropriate nucleophiles. The macromonomers were copolymerized with N-vinyl-2-pyrrolidone (NVP), 2-hydroxyethyl methacrylate (HEMA) and isoprene (Is). Two types of graft copolymers were obtained: the first one is constituted of hydrophilic backbone (polyNVP or polyHEMA) and hydrophobic uniform polyTBA side chains. The second type is composed of a flexible hydrophobic polyIs backbone and hard hydrophobic polyTBA side chains which, however, become water swellable after quaternization.     

ABA type block copolymers of poly(monobutyl itaconate) and poly(monocyclohexyl itaconate) with poly(dimethylsiloxane): Synthesis and characterization

Monoesters of itaconic acid (monobutyl itaconate and monocyclohexyl itaconate) were synthesized and used as monomers. Poly(monobutyl itaconate) (PMBI) and poly(monocyclohexyl itaconate) (PMCHI) were prepared by free radical polymerization of these monomers using tert‐butyl hydroperoxide as initiator. Subsequently, ABA type block copolymers where the A block is PMBI or PMCHI and the B block is poly(dimethyl siloxane) (PDMS) were synthesized by free radical polymerization using a macroinitiator (diperoxycarbamate) containing PDMS units. The structural formulae of the products were confirmed by spectral analysis. The molecular weights of the products are not high. Therefore the mechanical and physical properties are rather poor. However, porous structures of copolymers are observed by means of SEM.     

Block copolymers of fluoral oligomer with urethanes: Preparation and thermal properties

Two series of block copolymers have been synthesized comprising of soft polytrifluoroacetaldehyde (polyacetal) segments and of hard 4,4′-methylenedi(phenyl isocyanate)/cis-cyclohexane-1,4-diol polyurethane segments. The series-A copolymers in which the soft segments were directly bound to the hard segments had significantly lower thermal stability than the series-B copolymers in which the soft segments were linked to the hard segments by sebacic ester units. In both series the thermal stability decreased with increasing soft segment content. The series-A copolymers exhibited two thermal transitions both characteristic of T_g's and separated by about 60 K. In contrast the series-B copolymers exhibited two characteristic T_g's separated by 200–250 K, depending on composition, together with an additional endothermic transition at about ambient temperature. All transitions for both series decreased with increasing soft segment content. The observations have been compared with those of other polyether and polyester based polyurethanes.     

Synthesis and characterization of liquid crystalline (norbornene-block-acetylene) block copolymers

We report the synthesis and characterization of block copolymers of mesogenic acetylene and norbornene moieties. As monomers, a norbornene derivative with cyanostilbenyl side groups and an acetylene derivative with a cholesteryl group were used. The almost quantitative polymerization is initiated with the well-defined Schrock-type molybdenum carbene Mo(CH-t-Bu)(NAr)(O-t-Bu)₂ with NAr = 2,6-diisopropylaniline, t-Bu = tert-butyl. Polydispersity indices (PDIs) in the range of 2 for the block copolymers are obtained. The thermal and morphological behaviour of the polymers is characterized by means of differential scanning calorimetry (DSC) and X-ray diffraction. Both homo- and copolymers form thermotropic mesophases, the acetylene polymer exhibiting a smectic A phase, while the polynorbornene is nematic. The block copolymer shows microphase separation retaining the homopolymers' mesophases. To our knowledge, the materials presented here are the first example of phase-separated block copolymers of two side chain liquid crystalline polymers.