Synthesis and characterization of high molecular weight branched PBA

We prepared carboxylic acid group terminated linear polybutylene adipate (PBA) by melt polycondensation of adipic acid with 1,4‐butanediol in the presence of titanium(IV) isopropoxide (TIP) as a catalyst. High molecular weight branched PBAs were synthesized through the branching reaction between the carboxylic acid group terminated PBA and branching agent such as glycerol or pentaerythritol in the presence of TIP. The weight‐average molecular weights of the branched PBAs were found to be in the range of about 100,000–240,000 by gel permeation chromatography. Mechanical properties of the linear and branched PBAs were measured on an Instron tensile tester. The moduli of the branched PBAs had lower values of 320–450 MPa than those of the linear PBAs, whereas the elongations at break of the branched PBAs were in the range of 530–590%, which are much greater than the linear PBAs. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2143–2150, 2001     

Synthesis and characterization of high molecular weight carboxylated polybutadiene

High molecular weight carboxylated polybutadienes (cPBDs) with number-average molecular weight (M_n) from 98,000 to 200,000 and carboxylic acid (COOH) contents of 0.5–10 mol % were successfully synthesized through hydrocarboxylation of polybutadienes (PBDs) at temperatures of 140–150°C using PdCl₂(PPh₃)₂ and SnCl₂ · 2H₂O catalysts. At low extents of hydrocarboxylation (COOH < 6 mol %), glass transition temperatures (T_g's) of the resulting cPBDs did not change considerably (<10°C). Significant chain scission and crosslinking was not detected during the chemical modification process. Characterization of the microstructures of cPBDs by FTIR, ¹³C-NMR, and Raman spectroscopy showed that the carboxylic groups were incorporated on the pendant (1,2) PBD double bonds as well as the backbone (1,4) double bonds, indicating the hydrocarboxylation reaction did not solely occur at the terminal carbons of the pendant double bonds. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3129–3138, 1999     

磺化聚苯醚离聚体微乳化过程相反转的研究

以乙酰磺酸为磺化剂制备了磺化度为 3%～ 1 7%mol的磺化聚苯醚 (SPPO)并中和成盐 ,在一定的温度和搅拌速度下 ,加水将SPPO乳化成水包油的稳定水基微乳液。用乳化过程中的体系的电导率、粘度和表面张力的变化表征了乳化相反转过程。另外还研究了溶剂的极性和离子含量对SPPO溶液可乳化性和乳化过程的影响     

Phase behavior of low molecular weight polyethylenes from homogeneous and heterogeneous solutions

The pseudophase diagrams of solutions of low molecular weight polyethylene (PE) (number‐average molecular weight < 1500 g/mol) in octamethyl cyclotetrasiloxane (OCTS) and isododecane (IS) were determined by direct observation of cloud points and optical microscopy. In addition, melting temperatures were also determined by differential scanning calorimetry. In the range of single liquid–solid transitions, the data conformed to the classical melting temperature composition relation as a result of the formation of extended crystallites. The melting data were used to determine the interaction parameter of the PE in OCTS (1.4 ± 0.1) and IS (0.22 ± 0.05). The structural and thermal properties of the gels formed by a competing liquid–liquid and liquid–solid phase separation, under nonequilibrium conditions, contrast with the properties of the crystals formed from a single liquid–solid transition. Coarsening within the liquid phases was evidenced by optical microscopy, and insights about the mechanism of the kinetics of the coarsening process are given. The temporal changes of the melting temperature of crystallites formed from the heterogeneous phase (OCTS) reveal dynamics within a nonequilibrium state. In contrast, the crystallites formed from a homogeneous solution (IS) showed negligible melting‐temperature changes with time. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 878–889, 2002     

Synthesis and Characterization of Sulfonated Polyphosphazene-graft-Polystyrene Copolymersfor Proton Exchange Membranes简

A novel series of polyphosphazene-grafl-polystyrene （PP-g-PS） copolymers were successfully prepared by atom transfer radical polymerization （ATRP） of styrene monomers and brominated poly（bis（4-methylphenoxy）phosphazene） macroinitiator. The graft density and the graft length could be regulated by changing the bromination degree of the macroinitiator and the ATRP reaction time, respectively. The PP-g-PS copolymers readily underwent a regioselective sulfonation reaction, which occurred preferentially at the polystyrene sites, producing the sulfonated PP-g-PS copolymers with a range of ion exchange capacities. The resulting sulfonated PP-g-PS membranes prepared by solution casting showed high water uptake, low water swelling and considerable proton conductivity. They also exhibited good oxidative stability and high resistance to methanol crossover. Morphological studies of the membranes by transmission electron microscopy showed clear nanophase-separated structures resulted from hydrophobic polyphosphazene backbone and hydrophilic polystyrene sulfonic acid segments, indicating the formation of proton transferring tunnels. Therefore, these sulfonated copolymers may be candidate materials for proton exchange membranes in direct methanol fuel cell （DMFC） applications.     

Determination of molecular weight dependences and characterization of molecular weight distributions

Molecular weight dependences of the square of the radius of gyration as well as of the coefficients of diffusion and friction of monodisperse polystyrenes in toluene at 20°C are determined experimentally. For this purpose, the z-averages of these quantities and $\text{M}$_w as determined by light scattering were subjected to the polydispersity correction procedures as described previously. In addition, a method is suggested for the checking of known data with respect to molecular weight distribution, using measured values in conjunction with the polydispersity correction procedures.     

Purification and characterization of a native zinc-binding high molecular weight multiprotein complex from human seminal plasma

The seminal plasma comprises secretions from various accessory sex glands. During fertilization spermatozoa undergo complex sequences of precisely timed events that are regulated by the activation of different intracellular signaling pathways. The precision and efficacy of these pathways are often influenced by the assembly and interactions of multiprotein complexes, thereby directing the flow of regulatory information. Our knowledge about these protein complexes present in human seminal plasma (HuSP) is limited. Here we report the identification and characterization of a native high molecular weight zinc-binding multiprotein complex from HuSP by utilizing 2-DE followed by MS. Twenty-six proteins representing isoforms and/or fragments of 11 different proteins were found to be assembled in this complex. Prostate-specific antigen, zinc α2-glycoprotein, prostatic acid phosphatase, and prolactin inducible protein were the major proteins of this complex. Dynamic light scattering experiments revealed changes in aggregation pattern accompanied with deviation from physiological pH and in presence of SDS. However, no significant changes were observed in the presence of physiological ligands such as zinc and fructose. The present study will be useful and contribute to guide the future studies performed for elucidation of biological significance of this native complex in HuSP.     

Synthesis and characterization of sulfonated polyimide membranes for direct methanol fuel cell

The sulfonated polyimide (SPI) membranes for direct methanol fuel cell (DMFC) were synthesized with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 2,2′-benzidinedisulfonic acid (BDSA), 4,4′-oxydianiline (ODA) through classical two-step methods: (1) preparation of sulfonated poly(amic acid) (SPAA) precursors with different sulfonation levels by controlling the molar ratio of BDSA to ODA, and (2) thermal imidization of the SPAA films. The chemical structure and the imidization from SPAA membranes were characterized by FT-IR with temperature, and the sulfonation levels were determined by elemental analysis. The thermal stability of the membranes was also characterized by TGA. From water uptake and small angle X-ray scattering (SAXS) experiments for different sulfonation levels, it was found that the number of water clusters in SPI membranes increased as the water uptake of membranes increased, but the size of water cluster was not changed with the sulfonation levels. The proton conductivity and the methanol permeability of SPI membrane showed a sudden leap like a percolation phenomenon around 35 mol% of sulfonation level. The SPI membranes exhibited relatively high proton conductivity and extremely low methanol permeability, and showed the feasibility of suitable polymer electrolyte membranes (PEM) for DMFC.     

Synthesis and characterization of linear high molecular weight poly(amino-s-triazine)s

A two-phase polycondensation reaction was used to prepare high molecular weight linear poly-(amino-s-triazine)s from aminodichloro-s-triazines and diamines. These polymers contain a high concentration of melamine-type units in the polymer backbone. Molded specimens exhibited good mechanical properties and resistance to organic solvents. Dimethyl substitution at the exocyclic amino group led to a significant reduction in indentation resistance, strength, and modulus.     

Synthesis and characterization of sulfonated poly(phthalazinone ether phosphine oxide)s by direct polycondensation for proton exchange membranes

A series of sulfonated poly(phthalazinone ether phosphine oxide)s (sPPEPO) were prepared via aromatic nucleophilic substitution polycondensation of 4‐(4‐hydroxyphenyl) phthalazinone (HPPZ) with sulfonated bis(4‐fluorophenyl)phenyl phosphine oxide (sBFPPO) and bis(4‐fluorophenyl)phenyl phosphine oxide (BFPPO) at various ratios. The properties such as molecular weight, ion exchange capacity (IEC), swelling, thermal stability, proton conductivity, and morphology were investigated. sPPEPO with high IEC exhibited high proton conductivity while they still showed low swelling. Typically, sPPEPO with IEC of 1.54 and 1.69 meq/g exhibited high conductivity of 0.091 and 0.19 S/cm, and low swelling ratios of 14.3% and 19.5% at 80 °C, respectively. The low swelling was attributed to the strong intermolecular interaction including the electrostatic force and hydrogen bond. sPPEPO would be promising candidates used as polyelectrolyte membranes for fuel cells. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1758–1769, 2008     

Ultra-drawing of high molecular weight polyethylene cast from solution

Summary Hot drawing of high molecular weight polyethylene ( ) was studied. It was found that solutioncast films exhibited a drastically increased drawability in comparison with melt-crystallized material. This phenomenon, which enabled the production of polyethylene structures with a Young's modulus of 108 GPa and a strength of 3.0 GPa, is discussed in terms of a reduced number of entanglements in solution-crystallized material related to melt-crystallized films.With 2 figures and 1 table     

Development and characterization of crosslinked ionomer membranes based upon sulfinated and sulfonated PSU crosslinked PSU blend membranes by alkylation of sulfinate groups with dihalogenoalkanes

Crosslinked sulfonated PSU blend membranes have been produced via a new crosslinking process. The blends have been obtained from mixing of PSU Udel^tm Na-sulfonate and PSU Udel^tm Li-sulfinate in N-methyl pyrrolidone. The membranes have been crosslinked by S-alkylation of PSU sulfinate groups with dihalogenoalkanes The membranes produced via this process have been characterized in terms of ion-exchange capacity, electric resistance, swelling, ion-permselectivity. In addition, the thermal stability of the membranes has been determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and FTIR-spectra of the prepolymers and of the crosslinked blend membranes have been recorded. The new crosslinking procedure shows following advantages: (i) the preparative effort for crosslinking is very low; (ii) the properties of the crosslinked membranes are reproducible; (iii) the crosslinking proceeds with a high yield when applying suitable dihalogenoalkanes or other crosslinkers which are capable to S-alkylate the sulfinate group. The properties of the crosslinked PSU blend membranes are: (i) low electrical resistance at high IEC's; (ii) low swelling rate in practical temperature ranges from 20–70°C; (iii) excellent hydrolysis stability; (iv) excellent thermal stability.     

Steam-cracking of high molecular weight paraffins

Solid paraffins were steam-cracked in order to imitate the pyrolysis of low polymerization grade polyethylene. The behavior of the paraffins in steam-cracking corresponds to that of gasolines due to the similar C/H ratio.     

Synthesis and characterization of nylon-grated polyphenylene ether

Polyphenylene ether (PPE) resin (a homopolymer made from 2,6-xylenol with an i.v. of 0.46) was reacted with phenyl acrylate, p-substituted phenyl acrylates, and diphenyl fumarate in an extruder or in solution. The number of olefinic molecules that had been grafted onto the PPE backbone was determined by FTIR or NMR methods, and the grafting efficiency and mechanism were examined. The grafted PPE resins were used to promote the anionic polymerization of ε-caprolactam, and the quantity and the composition of the PPE–nylon 6 copolymers isolated were correlated with the number of promoter groups attached to the PPE resin.     

Polyurethane and sulfonated polysulfone blend ultrafiltration membranes. I. Preparation and characterization studies

Polyurethane (ether type) and sulfonated polysulfone (sodium salt form) in the presence of polyethylene glycol 600 were blended in various compositions using N,N'-dimethylformamide as solvent and used for preparing ultrafiltration membranes by the phase inversion technique. Polymer blend composition, additive concentration, and casting and gelation conditions were optimized. Blend membranes were subjected to ultrafiltration characterizations such as compaction, pure water flux, water content, and membrane resistance. The membranes were also subjected to the determination of pore statistics and molecular weight cutoff determination studies using dextran of different molecular weights. Surface morphology of the membranes was analyzed using scanning electron microscopy at different magnifications. The effects of polymer composition and additive concentration on the above parameters were analyzed and the results are compared and discussed with those of pure sulfonated polysulfone membranes. The derived pore size, porosity, and number of pores have a remarkable interrelationship and also have a definite role and relationship with the molecular weight cutoff, morphology, and flux performance of the membranes.     

Synthesis and characterization of dimethacrylate monomer with high molecular weight for root canal filling materials

A new dimethacrylate monomer 9,9'-bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)phenyl] fluorene (3) with a molecular weight of 634 was synthesized in 51.4% yield by addition of a glycidyl ether group to 9,9'-bis(4-hydroxyphenyl) fluorene (1) by the reaction of compound 1 with epichlorohydrin, and then introducing the methacrylate moiety by the reaction of the epoxy group with methacrylic acid. The structure of monomer 3 was confirmed by FT-IR, (1)H-NMR, mass spectra and elemental analysis.     

Development of injectable high molecular weight hyaluronic acid hydrogels for cartilage regeneration

The study focuses on developing hyaluronic acid (1200 kilo Dalton) hydrogels for cartilage regeneration. In spite of being highly biocompatible; a large amount of water absorption and easily degrading nature restricts the use of hyaluronic acid in the field of tissue regeneration. This can be rectified by crosslinking hyaluronic acid with a crosslinking agent such as divinyl sulfone; which results in a biocompatible hydrogel with superior rheological properties. Different amounts of divinyl sulfone have been used for crosslinking hyaluronic acid to get three types of hydrogels with differing properties. Swelling studies, rheology analysis, enzymatic degradation and scanning electron microscopic analysis were conducted on all the different types of hydrogels prepared. Viscoelastic properties of the hydrogel were analyzed so that a hydrogel with better elastic property and stability is obtained. Scanning electron microscopy was used to study the morphology of the HA hydrogels. The cytotoxicity testing was conducted to prove the non-toxic nature of the hydrogels and cell culture studies using adipose mesenchymal stem cells showed better adhesion and proliferation properties in all the three hydrogels. Thus hyaluronic acid hydrogel makes a promising material for cartilage regeneration.