Zhiqiang Sun

Water soluble polyaniline and its blend films prepared by aqueous solution casting

Polyaniline (PAn) was doped with phosphonic acid containing hydrophilic tails. The solubility of the doped PAn in water was controlled by changing the length of hydrophilic chain in the dopant. When poly(ethylene glycol) monomethyl ether (PEGME) with molecular weight M-w = 550 was used as the hydrophilic chain of the dopant, the doped PAn was entirely soluble in water. The film cast from aqueous solution showed good electrochemical redox reversibility, Aqueous solution blending of PAn with poly(ethylene glycol) (PEG, M-w = 20 000) and poly(N-vinyl pyrrolidone) (PVP, M-w = 360 000) was achieved. Percolation threshold of the composite film was lower than 3 wt.%. Electrical conductivity of the composite film was in the range of 10(-1)-10(-5) S cm(-1), depending on molecular weight of the acid and the content of PAn in the composite

Synthesis and characterization of half-salen complexes and their application in the polymerization of lactide and epsilon-caprolactone

A series of half-salen ligands and their aluminum Al(III) complexes that contained different substituents were designed and synthesized. All the ligands and their complexes were characterized by 1H, 13C NMR and elemental analysis. The complexes can be used as catalysts to produce polylactide and poly-e-caprolactone. All polymerizations were living with narrow molar mass distributions. The Mn(obsd) values of the isolated polymers were in good agreement with Mn(calcd). The polymerization rate of the electrophilic substituted complex was higher than the non-electrophilic substituted analogues. The more bulky substituents with more steric hindrance of the complexes showed relatively low polymerizing activity. The aluminum complexes showed a moderate stereo-selectivity to the ring opening polymerization of rac-lactide to give isotactic enriched polylactide.

Bimetallic Schiff-base aluminum complexes based on pentaerythrityl tetramine and their stereoselective polymerization of racemic lactide

A series of Schiff base aluminum(III) complexes with bimetallic active centers are synthesized. Their catalytic properties in the solution polymerization of racemic lactide (rac-LA) are examined. The modifications in the auxiliary ligand exhibited a dramatic influence on the catalytic performance. Among these complexes, 3a has the highest stereoselectivity (Pm = 0.91) owing to the bulky tert-butyl groups on the salicylaldehyde. Kinetic studies indicate that the polymerizations are both first-ordered with respect to the monomer and catalyst. Other factors that influence the polymerization such as the polymerization time and the temperature, as well as the monomer concentration, are discussed in detail.

Bimetallic Schiff base complexes for stereoselective polymerisation of racemic-lactide and copolymerisation of racemic-lactide with ε-caprolactone

Three pairs of bimetallic Schiff base aluminum complexes (1a–6a) with different tetraamine backbone bridging parts and bulky silyl-substituted moieties on salicylidene were synthesized. Using these complexes as catalysts for ring opening polymerisation (ROP) of racemic-lactide (rac-LA), systematical stereoselectivity and kinetic studies on ROP of rac-LA were carried out. The Gibbs free energy difference between homo-propagation and cross-propagation (ΔG≠) calculated by activation entropy and enthalpy showed that bulky substituents at the 3-position enhanced the stereoselectivity. And the kinetic study results indicated that bulkier substituents with more steric hindrance reduced the ROP reactivity. Moreover, these complexes could also be used for copolymerisation of rac-LA and e-caprolactone (e-CL). Copolymers of poly(LA-co-CL) with various monomer ratios were synthesized. Kinetic research on copolymerisation as well as microstructure analysis demonstrated that poly (LA-co-CL) achieved by these complexes were tapered block copolymers.

Synergistic effect of PLA–PBAT–PLA tri-block copolymers with two molecular weights as compatibilizers on the mechanical and rheological properties of PLA/PBAT blends

Two types of polylactide–poly(butylene adipate-co-terephthalate)–polylactide (PLA–PBAT–PLA) tri-block copolymers with different molecular weights (CP1 and CP2) were synthesized as compatibilizers for PLA/PBAT blends. Synergistic effects of CP1 and CP2 on the mechanical and rheological properties of the blends have been studied in detail. The addition of small amounts of CP1 and CP2 remarkably increased the elongation at the break point. 0.5 and 0.5 wt% of CP1 and CP2 led to an increase of elongation by over eightfold. Thermal, morphological and rheological analyses showed that addition of CP1 and CP2 increased the miscibility and interfacial bonding strength between PLA and PBAT, in addition to decreasing the melt viscosity. It was thought that the low-molecular-weight compatibilizer CP1 with high mobility would have a positive effect during the transportation of the high-molecular-weight CP2 from the matrix to the interface. In addition, CP2 played a key role in improving the interaction at the interface.

Highly stereoselective bimetallic complexes for lactide and ε-caprolactone polymerization

A series of Schiff-base compounds containing bimetallic ligands and two aluminum centers have been synthesized and characterized by 1H, 13C NMR and elemental analysis. These compounds could be successfully used as catalysts for the polymerization of rac-lactide and e-caprolactone. The polylactides (PLAs) prepared with these compounds were highly isotactic enriched (Pm = 0.97). The nature and steric hindrance of the ligands coordinated to the central metal ions remarkably influenced the polymer properties. Kinetic studies revealed that the polymerization was first order with respect to each of these compounds and lactide/caprolactone monomers. All the polymerizations were living, with good molecular weight control and relatively narrow molar mass distributions.

Synthesis, Characterization and Application of Methyl 3,5-Disulfo-benzoate Dipotassium Dihydrate as Nucleating Agent for Poly(L-lactide)

A newly synthesized aromatic sulfonate compound, complex 2 with formula of K2[H3COOC-C6H3(SO3)2]·2H2O(methyl 3,5-disulfo-benzoate dipotassium dihydrate) was synthesized and characterized by elemental analysis, infrared(IR) spectrometry, nuclear magnetic resonance(NMR) and crystal structure measurement. Single-crystal X-ray diffraction(XRD) revealed that complex 2 crystallized in the triclinic system with space group

Thermal, morphological, mechanical and aging properties of polylactide blends with poly(ether urethane) based on chain-extension reaction of poly(ethylene glycol) using diisocyanate

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