Novel polyimides derived from 2,3,3 ',4 '-benzophenonetetracarboxylic dianhydride

A series of polyimides (PIs) based on 2,3,3',4'-benzophenonetetracarboxylic dianhydride (2,3,3',4'-BTDA) and 3,3',4,4'-BTDA were prepared by the conventional two-step process. The properties of the 2,3,3',4'-BTDA based polyimides were compared with those of polyimides prepared from 3,3',4,4'-BTDA. It was found that PIs from 2,3,3,4'-BTDA have higher glass transition temperature and better solubility without sacrificing their thermal properties. Furthermore the theological properties of PMR-15 type polyimide resins based on 2,3,3',4'-BTDA showed lower melt viscosity and wider melt flow region (flow window) compared with those from 3,3',4,4'-BTDA. The structure-property relations resulted from isomerism were discussed.

Polyimides from isomeric oxydiphthalic anhydrides

2,2',3,3'-Oxydiphthalic dianhydride (2,2',3,3'-ODPA) and 2,3,3',4'-ODPA were synthesized from 3-chlorophthalic anhydride with 2,3-xylenol and 3,4-xylenol, respectively. Their structures were determined via single-crystal X-ray diffraction. A series of polyimides derived from isomeric ODPAs with several diamines were prepared in dimethylacetamide (DMAc) with the conventional two-step method. Matrix-assisted laser desorption/ionization time-of-flight spectra showed that the polymerization of 2,2',3,3'-ODPA with 4,4'-oxydianiline (ODA) has a greater trend to form cyclic oligomers than that of 2,3,3',4'-ODPA. Both 2,2',3,3'-ODPA and 2,3,3',4'-ODPA based polyimides have good solubility in polar aprotic solvents such as DMAc, dimethylformamide, and N-methylpyrrolidone. The 5% weight-loss temperatures of all polyimides were obtained near 500 degreesC in air. Their glass-transition temperatures measured by dynamic mechanical thermal analysis or differential scanning calorimetry decreased according to the order of polyimides on the basis of 2,2',3,3'-ODPA, 2,3,3',4'-ODPA, and 3,3',4,4'-ODPA. The wide-angle X-ray diffraction of all polyimide films from isomeric ODPAs and ODA showed some certain extent of crystallization after stretching. Rheological properties revealed that polyimide (2,3,3',4'-ODPA/ODA) has a comparatively lower melt viscosity than its isomers, which indicated its better melt processability.

Cationic cyclization of neoprene with a diethylaluminum chloride and organic chloride catalyst system

The cyclization of neoprene was achieved with the aid of a cationic catalyst system based on diethylaluminum chloride (Et2AlCl) and an organic chloride, allyl chloride (CH2=CHCH2Cl) or benzyl chloride (C6H5CH2Cl). The main parameters of the cyclization process were investigated. Elastomers with low intrinsic viscosity, ready solubility and some gelling were obtained. Xylene was a good solvent for the cyclization process, which took place in a very short time (less than or equal to5 min). The products were characterized with IR, H-1-NMR, differential scanning calorimetry, and gel permeation chromatography. The polycyclic structure was determined. The degree of cyctization and the incorporated solvent content were estimated with a H-1-NMR method.

Vinylic polymerization of norbornene by neutral nickel(II)-based catalysts

Neutral Ni(II) salicylaldiminato complexes activated with modified methylaluminoxane as catalysts were used for the vinylic polymerization of norbornene. Catalyst activities of up to 7.08 x 10(4) kg(pol)/(mol(Ni) (.) h) and viscosity-average molecular weights of polymer up to 1.5 x 10(6) g/mol were observed at optimum conditions. Polynorbornenes are amorphous, soluble in organic solvents, highly stable, and show glass-transition temperatures around 390 degreesC. Catalyst activity, polymer yield, and polymer molecular weight can be controlled over a wide range by the variation of the reaction parameters such as the Al/Ni ratio, monomer/catalyst ratio, monomer concentration, polymerization reaction temperature, and time.

Silane bridged polymerized metallocene catalyst for ethylene polymerization

The polymerized metallocene catalyst 4 was prepared by the co-polymerization of ansa-zirconocene complex [CH3Si(2)]ZrCl2 (3) containing vinyl substituted silane bridge with styrene in the presence of radical initiator. Catalyst 4 was found to display high ethylene polymerization activity of 2.28 x 10(6) g PE/(mol . h) with a viscosity average molecular weight (M-eta) value of 61.6 x 10(3) using methylalumoxane (MAO) as a co-catalyst. The ethylene polymerization has been investigated under different conditions.

Oriented crystallization process of polypropylene fractions

Melting recrystallization processes of melt-sheared films of polypropylene (S28C) fractions have been investigated in situ by polarized optical microscope equipped with CCD camera and hot-stage. Actually, the morphological developments in the melting recrystallization are partially reappearance of oriented crystallization processes during melt-shearing the fractions, which is due to a memory effect of oriented structure of polymer. For low molecular weight fraction, only incomplete spherulites with some orientation along shear direction are observed in the melting recrystallization processes of the sheared films. For middle molecular weight fractions, extended chain fiber crystals(or bands) are formed first at higher temperatures, and the bands can act as self-nuclei (i. e., row nuclei), resulting in epitaxial growth of chain-folded lamellae(or fibril), i. e., the formation of cylindrites, with further decrease of the crystallization temperature. For high molecular weight fraction, however, it is not possible to shear the melt film because of its high melt viscosity. When the low molecular weight fraction in which no fiber crystals or cylindrites are observed, are mixed with small amount(about 1%-2%) of the high molecular weight fraction, quite large number of cylindrites are formed during the melting recrystallization process of its sheared film, which implies that the component of high molecular weight plays an important role in the formation of cylindrites during the shear process of polypropylene.

Synthesis and characterization of aromatic dianhydrides and polyesterimides derived from 4-hydroxyphthalic anhydride

4-Hydroxyphthalic anhydride, prepared from 4-chlorophthalic anhydride, was reacted with trimellitic anhydride monoacid chloride or arylene diacid chloride to give aromatic ester-containing dianhydrides (EDAs). These dianhydrides were characterized by element analysis, melt point, FTIR and H-1-NMR. A series of aromatic poly (amic ester acid)s was synthesized by polycondensation of these EDAs and various diamines in polar organic solvent. The inherent viscosity of poly (amic ester acid)s ranged from 0.55 to 0.89 dL/g, indicating the intermediate to higher molecular weight. Polyesterimides having glass transition temperatures between 184-219degreesC were produced by thermal imidization of corresponding poly (amic ester acid)s. These polymers were fairly resistant to organic solvent, but some of them were soluble in phenol solvents. Thermogravimetric analyses revealed that these polyesterimides were stable up to 400degreesC, and the 5% weight loss temperatures were recorded in the range of 432-483degreesC in air atmosphers and 451-490degreesC in nitrogen.

Cationic cyclization of styrene-butadiene rubber

Controlled cyclization of styrene-butadiene rubber (SBR) was achieved with the aid of cationic catalyst system based on diethylaluminium chloride (AIEt(2)Cl) and benzyl chloride (C6H5CH2Cl) and by working in xylene solution at high temperature (T > 100 degreesC). The main parameters of the cyclization process were investigated. Elastomers with low intrinsic viscosity, ready solubility, free gel were obtained. The products were characterized with IR H-1-NMR, DSC, GPC. The polycyclic structure was determined. (C) 2001 Published by Elsevier Science Ltd.

Study on a series of main-chain liquid-crystalline ionomers containing sulfonate groups

A series of main-chain Liquid-crystalline ionomers containing sulfonate groups pendant on the polymer backbone were synthesized by an interfacial condensation reaction of 4,4'-dihydroxy-alpha,alpha'-dimethyl benzalazine, a mesogenic monomer, with brilliant yellow (BY), a sulfonate-containing monomer, and a 1/9 mixture of terephthaloyl and sebacoyl dichloride. The structures of the polymers were characterized by LR and UV spectroscopies. DSC and thermogravimetric analysis were used to measure the thermal properties of those polymers, and the mesogenic properties were characterized by a polarized optical microscope, DSC, and wide-angle X-ray diffraction. The ionomers were thermally stable to about 310 degreesC. They were thermotropic liquid-crystalline polymers (LCPs) with high mesomorphic-phase transition temperatures and exhibited broad nematic mesogenic regions of 160-170 degreesC, and they were lyotropic LCPs with willowy leaf-shaped textures in sulfuric acid. However, the thermotropic liquid-crystalline properties were somewhat weakened because the concentration of BY was more than 8%. The inherent viscosity in N-methyl-2-pyrrolidone suggested that intramolecular associations of sulfonate groups occurred at low concentration, and intermolecular associations predominated at higher concentration. (C) 2001 John Wiley & Sons, Inc.

Diffusion-limited kinetics modeling of one-step polyimide formation

A diffusion-limited kinetic model was developed to describe the imidization of one-step polythioetherimide formation based on an endgroup diffusion model. The changes of conversion and viscosity during the imidization were monitored with thermogravimetric analysis and dynamic stress rheometry, respectively. It was observed that the imidization rate began to decelerate after a fast early stage, whereas the viscosity in the system increased dramatically after a period of low value. Amic acid and imide formations concurrently take place in the one-step polyimide formation, but the formation of amic acid is much slower than that of imide and is the rate-limiting step of imidization. When a second-order kinetic model was used to describe the imidization, the effect of viscosity on the diffusion resistance of reactive groups needed to be included. In order to predict the change of viscosity during the imidization, the Lipshitz-Macosko model was modified and introduced into the diffusion-limited kinetic model by the Stokes-Einstein equation. The comparison of the modeled results with experimental data indicated that the diffusion-limited kinetic model and the modified Lipshitz-Macosko model were able to efficiently predict the changes of conversion and viscosity with temperature and time during the one-step polythioetherimide formation. (C) 2001 John Wiley & Sons, Inc.

Synthesis of a new kind of polyamide and polyester including aromatic spirodilactone

A new kind of monomers including aromatic spirodilactone-5, 5'-carboxy-7,7'-dioxo-2,2'-spirobi(benzo-[c]tetrahydrofuran) is synthesized from m-xylene and paraformaldehyde. It is converted to a series of polyamides and polyesters by means of low-temperature solution polycondensation and interfacial polycondensation. NMR and IR spectra, solubility, mechanical and thermal properties of all these polymers are investigated. The polymers have high glass transition temperatures and good thermal oxidative properties. All polyamides have high viscosity and good solubility in strong polar organic solvents such as DMSO, DMAc, DMF and NMP. All polyamides can be cast into transparent, flexible and tough films possessing good tensile properties.

Ester-type precursor of polyimide and photosensitivity

In order to investigate the influence of the main chain structure and molecular weight on the sensitivity of photosensitive ester-type precursor of polyimide (photo-PAE), an improved method was used to synthesize several kinds of photo-PAEs with relatively high molecular weight. Their sensitivities (at 365 nm) were investigated, and it was found that some additives such as sensitizer and photoinitiator had the greatest influence on the sensitivity of photo-PAE, that the photo-PAE with BPDA and mPDA as the main chain structure had the best sensitivity (D-0.5: 5-10 mJ/cm(2)) among the studied photo-PAEs, and that the sensitivity did not significantly change with the change of inherent viscosity of photo-PAE. Meanwhile, the thermal imidization of these photo-PAEs was also investigated by means of TGA and IR analyses. Additionally, a discussion was made for formulation of PSPI resist. (C) 1999 Elsevier Science Ltd. All rights reserved.

Synthesis and properties of optically active poly(amide-imide)s containing axially dissymmetric 1,1 '-binaphthyl moieties

Novel optically active aromatic poly(amide-imide)s (PAIs) containing 1,1'-binaphthyl-2,2'-diyl units in the main chain were prepared by polycondensation reactions of newly synthesized dianhydride, 2,2'-bis(3,4-dicarboxylzenzamido)-1,1'-binaphthyl dianhydride[(S)-BN-DADA and (+/-)-BNDADA], with diamines, The properties of the resulted PAIs were fully characterized by a combination of investigations on inherent viscosity, thermal properties(DSC and TGA), specific rotation, CD and UV-Vis absorbance. These PAIs showed good solubilities, thermal properties and optical stabilities. Interesting UV-Vis absorption behavior of films casted from these PAIs was observed and analyzed.

Syndiotactic polystyrene/thermoplastic polyurethane blends using poly(styrene-b-4-vinylpyridine) diblock copolymer as a compatibilizer

The effect of adding diblock copolymer poly(styrene-b-4-vinylpyridine) (P(S-b-4VPy), to immiscible blends of syndiotactic polystyrene (sPS)/thermoplastic polyurethane (TPU) on the morphology, thermal transition, crystalline structure, and rheological and mechanical properties of the blends has been investigated. The diblock copolymer was synthesized by sequential anionic copolymerization and was melt-blended with sPS and TPU. Scanning electron microscopy (SEM) showed that the added block copolymer reduced the domain size of the dispersed phase in the blends. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) revealed that the extent of compatibility between sPS and TPU affected the crystallization of the sPS in the blends. Tensile strength and elongation at break increased, while the dynamic modulus and complex viscosity decreased with the amount of P(S-b-4VPy) in the blend. The compatibilizing effect of the diblock copolymer is the result of its location at the interface between the sPS and the TPU phases and penetration of the blocks into the: corresponding phases, i.e. the polystyrene block enters the noncrystalline regions of the sPS, and the poly(4-vinylpyridine) block interacts with TPU through intermolecular hydrogen bonding. (C) 1999 Elsevier Science Ltd. All rights reserved.

Rheological, thermal, and morphological properties of ABS-PA1010 blends

Noncompatibilized and compatibilized ABS-nylon1010 blends were prepared by melt mixing. Polystyrene and glycidyl methacrylate (SG) copolymer was used as a compatibilizer to enhance the interfacial adhesion and to control the morphology. This SG copolymer contains reactive glycidyl groups that are able to react with PA1010 end groups (-NH2 or -COOH) under melt conditions to form SG-g-Nylon copolymer. Effects of the compatibilizer SG on the rheological, thermal, and morphological properties were investigated by capillary rheometer, DSC, and SEM techniques. The compatibilized ABS-PA1010 blend has higher viscosity, lower crystallinity, and smaller phase domain compared to the corresponding noncompatibilized blend. (C) 1999 John Wiley & Sons, Inc.