Synthesis and characterization of poly(ethylene glycol) grafted poly(L-lactide)

Poly(ethylene glycol) grafted poly(L -lactide) was prepared by ring opening polymerization of L -lactide and epoxy-terminated poly(ethylene glycol) methyl ether (PEGME). Stannous octoate and Al(Et)₃·0.5 H₂O were tested as polymerization catalysts, and Al(Et)₃·0.5 H₂O was found to be more effective for the ring-opening of the epoxy group of the modified PEGME monomer. The synthesized polymers were characterized by NMR and the efficiency of the incorporation of epoxy-terminated PEGME in the copolymer was determined.     

Synthesis and characterization of novel hyperbranched poly(imide silsesquioxane) membranes

A new family of hyperbranched polymers with chemical bonds between the hyperbranched polyimide and polysilsesquioxane network was synthesized by the reaction of an amine‐terminated aromatic hyperbranched polyimide with 3‐glycidoxypropyl trimethoxysilane, followed by hydrolysis and polycondensation in the presence of an acid catalyst. The hyperbranched poly(imide silsesquioxane) membranes were fabricated by the casting the aforementioned polymer solution onto a NaCl optical flat, which was followed by heating at 80 °C for 24 h. The membranes were characterized by Fourier transform infrared, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, N₂ adsorption and desorption, and CO₂ adsorption and desorption. The presence of covalent bonds between the hyperbranched polyimide and polysilsesquioxane segments had a significant effect on the properties of the membranes. N₂ adsorption–desorption isotherms for these membranes showed surface areas of 6–16 m²/g, whereas CO₂ adsorption–desorption isotherms showed much higher surface areas in the range of 106–127 m²/g. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3736–3743, 2003     

Synthesis and characterization of the B3-monomer and hyperbranched poly(aryl ether ketone)s

Hyperbranched poly(aryl ether ketone)s were prepared by polymerization of hydroquinone (A₂) and 1,3,5-tris[4-(4-fluorobenzoyl)phenoxy]benzene (B₃). The gelation of hyperbranched poly(aryl ether ketone)s was effectively avoided. Hydroxyl-term inated (HPAEK-OH) and fluoro-terminated (HPAEK-F) hyperbranched poly(aryl ether ketone)s were prepared by using different A₂/B₃ mass ratio. The structure of the B₃ monomer was confirmed by MS, ¹H NMR/IR. The glass transition temperatures of the HPAEK-F and HPAEK-OH are 114°C and 162°C respectively. Thermal stability of HPAEK-F is higher than HPAEK-OH. __________ Translated from Acta Scientianum Naturalium Universitatis Jilinensis, 2005, 5 (in Chinese)     

Synthesis and characterization of new hyperbranched poly(aryl ether oxadiazole)s

A new AB₂ monomer was synthesized for use in the preparation of a hyperbranched poly(aryl ether oxadiazole) with terminal phenol functionality. The AB₂ monomer contains two phenolic groups and a single aryl fluoride group that is activated toward nucleophilic displacement by the attached oxadiazole ring. The nucleophilic substitution of the fluoride with the phenolate groups led to the formation of an ether linkage. Subsequently, a hyperbranched poly(aryl ether oxadiazole) having approximately a 44% degree of branching, as determined by a combination of model compound studies and ¹H NMR, was obtained. The terminal phenolic groups underwent facile functionalization, furnishing hyperbranched polymers with a variety of functional chain ends. The nature of the chain‐end groups had a significant influence on the physical properties of the polymers, such as the glass‐transition temperature and their solubility. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3851–3860, 2001     

Synthesis and characterization of hyperbranched aromatic poly(ether imide)s with terminal amino groups

We synthesized an AB₂‐type monomer, 4‐{4‐[di(4‐aminophenyl)methyl]phenoxy}phthalic acid, which contained one phthalic acid group and two aminophenyl functionalities. The direct self‐polycondensation of the AB₂‐type monomer in the presence of triphenylphosphite as an activator afforded a hyperbranched poly(ether imide) with a large number of terminal amino groups. This polymer was characterized with ¹H NMR and IR spectroscopy. The degree of branching of the hyperbranched poly(ether imide) was approximately 56%, as determined by a combination of model compound studies and an analysis of ¹H NMR spectroscopy integration data. The terminal amino groups underwent functionalization readily. The solubility and thermal properties of the resulting polymers depended on the nature of the chain end groups. In addition, the hyperbranched poly(ether imide) was grafted with polyhedral oligomeric silsesquioxane (POSS). Transmission electron microscopy analysis revealed that the grafted POSS molecules aggregated to form a nanocomposite material. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3726–3735, 2003     

Synthesis and characterization of ultraviolet‐curable hyperbranched poly(siloxysilane)s

Two UV‐curable hyperbranched poly(siloxysilane)s ( I and III ) containing vinyl and allyl end groups were synthesized via polyhydrosilylation with methylbis(methylethylvinylsiloxy)silane and methylbis(dimethylallylsiloxy)silane monomers. A cationic UV‐curable hyperbranched polymer ( II‐Ep ) with epoxy end groups was prepared via the hydrosilylation of hyperbranched polymer II with Si? H terminated groups and glycidyl methacrylate, and II was also obtained via the polyhydrosilylation of AB₂‐type monomer methylvinylbis(methylethylsiloxy)silane. All hydrosilylation reactions were catalyzed by Pt/C or chloroplatinic acid. Three AB₂‐type monomers were synthesized via the hydrolysis of functional chlorosilane, which was prepared with Grignard reagents and dichlorosilane. The molecular structures of the polymers were characterized with ¹H NMR, Fourier transform infrared, and gel permeation chromatography, and the UV‐curing behaviors of the polymers under different atmospheres and with different photoaccelerators were also investigated. The thermostability of uncured and cured polymers was examined with thermogravimetric analysis, and the data indicated that the orders of the onset decomposition temperatures for the cured polymers and the residue weights were as follows: III (380 °C) > I (320 °C) > II‐Ep (280 °C) and I (70.4%) > III (64.1%) > II‐Ep (60.9%), respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1883–1894, 2005     

Preparation, characterization, and antimicrobial property of cotton cellulose fabric grafted with poly (propylene imine) dendrimer

Two generations of poly (propylene imine) dendrimer with amino terminated groups (G2- and G5-PPI-NH₂) were grafted on cotton cellulose fabric using cross linking agents (citric or glutaric acids). Fourier transform infrared (FTIR) spectroscopy identified ester groups which were formed between hydroxyl groups of the cotton fabric and carboxylic groups of the cross linking agents. Also, attenuated total reflectance-FTIR (ATR-FTIR) analysis confirmed formation of amide groups between the carboxylic groups of the cross linking agents and the amino end groups of the dendrimers. Nitrogen content (N-content) analysis revealed the presence of the dendrimers on the cotton fabric even after 5 washing cycles. In order to study the dispersion of the PPI dendrimers on the surface of the cotton fabric, field emission scanning electron microscopy (FE-SEM) was performed. The particle size distribution of the G2- and G5-PPI-NH₂ aqueous solutions was also determined by dynamic light scattering (DLS) analysis. Antimicrobial activity of the PPI dendrimer aqueous solutions and the cotton cellulose fabric grafted with the dendrimers was evaluated both quantitatively and qualitatively against Gram-positive bacterium (Staphylococcus aureus), Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli) and fungus (Candida albicans). The dendrimer grafted cotton cellulose fabric exhibited a 99 % reduction in bacterial counts against S. aureus, E. coli and C. albicans. The antimicrobial activities of the grafted cotton cellulose fabric with the PPI dendrimers were maintained even after 5 washing cycles.     

Synthesis and ionic conductivity of hyperbranched poly(glycidol)

A novel hyperbranched poly(glycidol) (HPG) was prepared and characterized. The synthesized HPG was used as a substrate of a polymer electrolyte. The ionic conductivity of a blend of HPG, polyurethane (PU), and salt was studied. The ionic conductivity of HPG/PU/LiClO₄ was about 6.6 × 10^?6 S · cm^?1 at 20 °C and 6.3 × 10^?4 S · cm^?1 at 60 °C. The results indicated that HPG showed higher solubility for salt than linear polyether when both had the same [O]/[Li⁺] molar ratio. The main reason was that more cavities and a lower degree of chain entanglement in HPG resulted in a lower glass‐transition temperature and were beneficial for decreasing the aggregation of salt or enhancing the ionic conductivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2225–2230, 2001     

Synthesis and characterization of poly(vinyl ferrocene) grafted hydroxyl-terminated poly(butadiene): A propellant binder with a built-in burn-rate catalyst

The graft copolymer hydroxyl-terminated polybutadiene-g-polyvinyl ferrocene (HTPB-g-PVF) was synthesized free radically from HTPB and vinyl ferrocene (VF) in benzene, using azobisisobutyronitrile as the radical initiator at 75°. The graft copolymer was analysed for its structural and thermal characteristics. The chemically bound ferrocene in HTPB-g-PVF, catalysis the oxygen up-take and oxidative degradation reactions of HTPB, and the mechanisms of the catalysis are discussed. The most probable grafting sites on HTPB and the mechanism of grafting also are discussed. The extent of the grafting, which was a function of VF concentration, was low. The graft copolymer also was tried as a propellant-binder-cum-burn-rate (BR) catalyst in a composite solid propellant, using toluene diisocyanate and trimethylol propane as curatives with dibutyl tin dilaurate as the curing catalyst, and the BRs of the propellants were evaluated at 3.9 MPa. The BRs increased with the extent of VF grafting but not proportionally. The BRs also were compared with those of reference HTPB propellants containing VF, Fe₂O₃, copper chromite, and so forth as BR catalysts. Chemically linked ferrocene in the binder augmented the propellant BR, probably because of the presence of catalytically active sites in the binder for its degradation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4090–4099, 1999     

Thermoresponsive poly(poly(ethylene glycol) methylacrylate)s grafted cellulose nanocrystals through SI-ATRP polymerization

We report a series of thermoresponsive cellulose nanocrystals (CNCs) decorated with poly(poly(ethylene glycol) methylacrylate) copolymers (poly(PEGMA)-g-CNCs) synthesized by surface initiated-atom transfer radical polymerization (SI-ATRP). The chemical structures and surface morphologies were subsequently confirmed by FT-IR, XPS, and AFM measurements. With regard to thermally responsive behavior, poly(PEGMA)-g-CNCs show tunable lower critical solution temperature (LCST) values in the range of 34–66 °C by varying the feeding ratios of comonomers. The reversible morphological transformation from individual nano-rod structures to larger globule aggregates was further verified by AFM during the LCST transition. These functionalized CNCs have potential as smart film filters and biosensors.     

SYNTHESIS AND PHOTOLUMINESCENCE OF AN ANTHRACENE-CONTAINING HYPERBRANCHED POLY（ARYLENEETHYNYLENE）

A hyperbranched poly（aryleneethynylene） containing anthracene chromophore was synthesized by palladiumcatalyzed cross-coupling reaction of 2,4,6-triiodophenyl 9-anthracenylcarboxylate with 9,9-bis[4-（2-propynyloxy）phenyl]- 9H-fluorene. The structure and properties of the polymer are characterized and evaluated by NMR, IR, UV, PL and TGA analyses. The polymer is soluble in common organic solvents, possesses high thermal stability （Td 〉 330℃）, and emits a strong blue light of 465 nm in both solution and solid states.     

Synthesis and characterization of two classes of hyperstar polymers bearing hyperbranched cores grafted with linear arms

New hyperstar polymers (HSP) consisting of two different hyperbranched (hb) aromatic/aliphatic cores grafted with linear polymer arms were successfully synthesized. The hb cores were based on either hb poly(vinylbenzylchloride) synthesized by SCVP‐ATRP or hb polyester from a polycondensation reaction. For the core‐first approach, the hb cores have been modified to hb macroinitiators initiating either the cationic ring‐opening polymerization of oxazolines (Oxa) or the atom transfer radical polymerization of alkylmethacrylates. For potential use as reactive binders in epoxy coatings the HSPs were equipped with a defined amount of OH‐groups during arm growth via controlled block‐copolymerization with nonfunctionalized and OH‐functionalized monomers, either an oxazoline (OH)Oxa (2‐[1‐(hydroxymethyl)ethyl]‐oxazoline) or a methacrylate HEMA (2‐hydroxyethyl methacrylate). The amount of OH‐groups could be well adjusted in this way. The hyperstars were comprehensively characterized with respect to chemical structure and molecule dimension. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 000: 000–000, 2012     

Synthesis and characterization of carboxymethylcelluloses (CMC) from non-wood fibers I.Accessibility of cellulose fibers and CMC synthesis

This paper explores the production of carboxymethylcellulose (CMC) fromseveral bleached cellulose pulps obtained from non-wood species. The chemicalcomposition (-cellulose, hemicellulose and lignin content), the degreeofswelling, viscosity, solubility in concentrated NaOH and crystallinity ofsoda/AQ cellulose pulps from abaca, jute, sisal, linen and Miscanthussinensis were determined. The pulps were carboxymethylated by one andtwo successive reaction steps in aqueous medium under identical conditions. Thedegree of substitution (DS) of CMC was found to be dependent upon the source ofthe cellulose pulp, but generally it was close to 1 with one etherificationtreatment and around 2 after the second. The molar mass of CMC was found to bedependent on the initial intrinsic viscosity of the cellulose pulp. The weightaverage molar mass of our CMCs ranged from 1.5×10⁵ to2.8×10⁵. Increasing the DS up to 2 improved the CMC solubility, butviscosity slightly decreased due to a slight degradation of the polymer.     

Synthesis of thermoresponsive polystyrene-based comb-type grafted poly(N-isopropylacrylamide)

Narrowly distributed polystyrene-g-p(N-isopropylacrylamide) (PSt-g-PNIPAM) was prepared by atom transfer radical polymerization (ATRP) of N-isopropylacrylamide using the brominated polystyrene as macroinitiator and CuCl combined with hexamethyltriethylenetetramine as catalyst. Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy confirmed the structure of PSt-g-PNIPAM. The gel permeation chromatography (GPC) showed that the graft copoly- mer had a single distribution peak with molecular weight, Mn (g/mol) of 19815 g/mol (using polystyrene as the standard). Differential scanning calorimetry (DSC) revealed that due to both effects of hydro- phobic isopropyl groups and hydrogen bonds in the amide group, the glass transition temperature (Tg) of PSt-g-PNIPAM enhanced 16.0 ℃ compared to the Tg of the polystyrene.     

Synthesis and intrinsic blue fluorescence study of hyperbranched poly(ester-amide-ether)

A series of hyperbranched poly(ester-amide-ether)s (H-PEAEs) were synthesized via the A₂+CB₃ approach by the self-transesterification of ethyl ester-amide-ethers end-capped with three hydroxyl groups and ethyl ester group at two terminals. The molecular structures were characterized with ¹H NMR and FT-IR spectroscopy. The number average molecular weights were estimated by GPC analysis to possess bimodal wide distribution from 1.57 to 2.09. The strong inherent blue fluorescence was observed at 330 nm for excitation and 390 nm for emission. Moreover, the emission intensity and fluorescence quantum yield increased along with the incorporated ether chain length, as well as almost linearly with the H-PEAE concentration in an aqueous solution. For comparing the fluorescence performance, the linear poly(ester-amide-ether) (L-PEAE) and hyperbranched poly(ester-amide) (H-PEA) were synthesized. The results showed that the coexistence of ether bond and carboxyl group in the molecular chain was essential for generating the strong fluorescence. However, the compact backbone of H-PEAE would be propitious to the enhancement of fluorescence properties.     

Synthesis of hyperbranched poly(ester urethane isocyanates) and their derivatives

Hyperbranched poly(ester urethanes) containing end isocyanate groups have been synthesized via the reaction of hyperbranched aliphatic polyesterpolydiols of three generations with tolylene diisocyanate. The interaction of these compounds with N,N-dimethylaminoethanol yields their functional derivatives. The polymers are characterized by functional analysis, ¹H NMR and IR spectroscopy, and DSC. It has been demonstrated that the incorporation of urethane moieties leads to development of the microheterogeneous structure of hyperbranched polymers.     

Synthesis and shape memory behavior study of hyperbranched poly(urethane-tetrazole)

A novel hyperbranched poly(urethane-tetrazole)(HPUTZ) was synthesized via the A2+BB2' approach using hexadiisocyanate(HDI) and 3-(bis-(2-hydroxyethyl)) aminopropyltetrazole(HAPTZ).The molecular structure was characterized by FTIR and 1H NMR spectroscopy.The number average molecular weight was measured to be 1.05×104 g/mol with a polydispersity of 1.27 by GPC analysis.The HPUTZ was further cured by the semi-adduct(PEG-IPDI) from polyethylene glycol(PEG) reacting with isophorone diisocyanate(IPDI) to form th...     

Preparation and characterization of poly(isobutyl methacrylate) microbeads with grafted amidoxime groups

Poly(isobutyl methacrylate) (PiBMA) microspheres with a 800- to 1500-μm diameter range synthesized by suspension polymerization technique were used as the trunk polymer in the preparation of a highly efficient new adsorbent. Glycidyl methacrylate (GMA) was grafted onto the trunk polymer by pre-irradiation grafting technique. Grafting conditions were optimized, and GMA grafted PiBMA beads were modified with iminodiacetonitrile (IDAN) in ethanol at 80 °C. The nitrile groups were then amidoximated by using 6% (m/v) hydroxylamine hydrochloride in methanol solution. The IDAN modification and the conversion of the nitrile groups to amidoxime were followed by FT-IR spectroscopy. The surface morphology and thermal behavior of the PiBMA and its modificated forms were also characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques further confirming modification and amidoximation.     

Preparation and characterization of electrospun fibers based on poly(L-lactic acid)/cellulose acetate

PLLA/CA mixtures of different compositions were successfully electrospun to obtain composite nanofibrous membranes.The microstructures of the membrances changed from homogeneous to heterogeneous with the addition of CA, which was observed by FE-ESEM.The PLLA/CA fabric membranes were characterized by mechanical testing,DSC and contact angle measurements.The tensile stress of the composite fibrous membranes increased obviously with the increase of CA content.DSC results indicated that the CA component was the main factor for the changes of enthalpies in the composite fibers.Contact angle measurements showed the hydrophilicity of the electrospun nanofiber membranes was improved with the addition of CA.