Polypyrrole (PPy)/montmorillonite (MMT) nanocompounds were prepared by in situ chemical oxidative polymerization of pyrrole in the presence of MMT. The results indicate PPy is intercalated into MMT interlayers and the morphology of obtained PPy in nanocompounds is changed to flake-like rather than granular particles as pristine PPy. The resultant PPy/MMT nanocompounds and pristine PPy were used as microwave absorbing filler separately to prepare microwave absorbing PPy/MMT and PPy epoxy composites. The results indicate PPy/MMT epoxy composites exhibit much better microwave absorbing properties than those filled by pristine PPy. The maximum reflection loss of 20 wt% PPy/MMT filled composite is −32.63 dB at 10.55 GHz with a matching thickness of 2.8 mm, and the effective absorption bandwidth with the reflection loss below −10 dB is from 8.6 GHz to 12.4 GHz, which almost covers the whole X-band. We postulated that the morphology change of PPy in PPy/MMT and its better dispersion may be responsible for the enhancement of microwave absorption. POLYM. COMPOS., 37:532–538, 2016. © 2014 Society of Plastics Engineers

Poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AA)) microspheres with a high copolymerized AA content were fabricated using rapid membrane emulsification technique. The uniform size, good hydrophilicity, and thermo sensitivity of the microspheres were favorable for trypsin immobilization. Trypsin molecules were immobilized onto the microspheres surfaces by covalent attachment. The effects of various parameters such as immobilization pH value, enzyme concentration, concentration of buffer solution, and immobilization time on protein loading amount and enzyme activity were systematically investigated. Under the optimum conditions, the protein loading was 493 ± 20 mg g⁻¹ and the activity yield of immobilized trypsin was 155% ± 3%. The maximum activity (V_max) and Michaelis constant (K_m) of immobilized enzyme were found to be 0.74 μM s⁻¹ and 0.54 mM, respectively. The immobilized trypsin showed better thermal and storage stability than the free trypsin. The enzyme-immobilized microspheres with high protein loading amount still can show a thermo reversible phase transition behavior. The research could provide a strategy to immobilize enzyme for application in proteomics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43343.

A new aromatic diamine containing trifluoromethyl and methyl groups, namely α,α-bis(4-amino-3-methylphenyl)-4-(trifluoromethyl)phenylmethane (1), was synthesized from 2-methylaniline and 4-(trifluoromethyl)benzaldehyde. A series of fluorinated polyimides (PIs) were prepared from the diamine with four commercially available aromatic tetracarboxylic dianhydrides using a one-step high-temperature polycondensation procedure. These obtained PIs showed excellent solubility, with the dissolvability at a concentration of 10 wt% in most solvents, and they could afford flexible and strong films. Thin films of these PIs exhibited high optical transparency and light color, with the cutoff wavelength at 324–357 nm and transmittance higher than 74% at 450 nm. Moreover, these PIs possessed eminent thermal stability and good mechanical properties.

A new unsymmetrical and noncoplanar diamine containing trifluoromethyl and trimethyl groups, 1,4-bis(4-amino-2-trifluoromethylphenoxy)-2,3,5-trimethylbenzene (2), was synthesized using 2,3,5-trimethylhydroquinone and 2-chloro-5-nitrobenzotrifluoride as starting materials. A series of fluorinated poly(ether imide)s (PEIs) (4a–4d) were prepared from diamine 2 with four aromatic dianhydrides via a one-step high-temperature polycondensation procedure. The obtained PEIs were readily soluble in most organic solvents and could be solution-cast into flexible and strong films. The resulting thin films exhibited light color and good optical transparency with a cutoff wavelength of 356–376 nm. They also displayed good thermal stability with glass transition temperatures (T_g) above 281°C, 10% weight loss temperatures in the range of 482–486°C, and the weight residue more than 55% at 800°C in nitrogen. Moreover, they revealed low dielectric constants (2.77–2.93 at 1 MHz) and low moisture absorptions (0.41%–0.57%).

A series of poly(ethylene terephthalate-co-4,4′-bibenzoate)s (PETBBs) were prepared via direct esterification from the monomers of terephthalic acid (TPA), 4,4′-biphenyl dicarboxylic acid (BPDA), and ethylene glycol (EG) with different molar ratios. The chemical compositions of the obtained PETBBs, investigated by H¹-NMR, were identical with the feed ratio, and the high molecular weights of PETBBs were confirmed by GPC analysis. The glass transition, crystallization, and melting behavior of them were measured by DSC; the results indicated that, in the range of 5–25 mol% of BPDA addition, the glass transition temperature (T_g) increased almost linearly and the melting temperature (T_m) decreased with increasing content of BPDA unit. As expected, the crystallization of PETBB became difficult with increasing introduction of BPDA, explained by higher crystallization temperature and smaller crystallization enthalpy from the glassy state. This decrease of crystallization rate may be beneficial to film processing. Moreover, owing to the introduction of rigid-rod BPDA unit, the initial and maximum thermal-oxidative decomposition temperatures were enhanced. The kinetic analysis of the thermal-oxidative degradation indicated that the apparent activation energies of degradation for these PETBBs became higher than that of PET. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

By introducing binary hydroxyl groups into poly(p-phenylene benzoxazole) (PBO) macromolecular chains, we synthesized dihydroxy poly(p-phenylene benzobisoxazole) (DHPBO) polymers and then prepared DHPBO fibers by dry-jet wet-spinning. Comparative studies were performed between intrinsic PBO fibers and DHPBO fibers. The effects of hydroxyl polar groups on improving the UV aging resistance of PBO fibers were investigated. With the introduction of hydroxyl groups, substantial changes in the chemical structures and surface morphologies of DHPBO fibers were observed. As proved by tensile testing and intrinsic viscosity measurement, the UV resistance of DHPBO fibers is obviously improved compared to that of intrinsic PBO fibers. XRD results indicate that the UV aging of these fibers occurs mainly on the surfaces of fibers. Based on these results, the mechanism of UV aging of PBO fibers was discussed. Copyright © 2009 John Wiley & Sons, Ltd.

Novel fluorinated polyimides were prepared from an unsymmetrical diamine, 3-methyl-4-(4-amino-2-trifluoromethylphenoxy)-4'-aminobenzophenone (3), with four aromatic dianhydrides via a one-step high-temperature polycondensation procedure. All the obtained polyimides were soluble in some polar solvents such as NMP, DMAc, and DMF. Flexible and tough films were prepared by casting from polymer solution. These polyimide films exhibited high optical transparency, good mechanical and thermal properties. Moreover, they possessed low dielectric constants and low-moisture absorption. Due to their properties, these fluorinated polyimides could be considered as photoelectric and microelectronic materials. Copyright © 2010 John Wiley & Sons, Ltd.

A series of novel polyamides 3a–3d containing 4-tert-butyltoluene moiety, were prepared using the phosphorylation polycondensation technique. FT-IR and ¹H NMR techniques were used to investigate the chemical structures of 3a–3d. The results confirmed that they agreed with the proposed structures for 3a–3d completely. The 3a–3d had inherent viscosities ranging from 0.71 to 1.67 dL·g⁻¹. All the polyamides showed excellent solubility, with the dissolvability at a concentration of 10 wt% in most amide polar solvents. Flexible and tough polyamide films could be prepared by casting from DMAc (N,N-dimethylacetamide) solvent. Their films were nearly colorless and exhibited high optical transparency, with the UV cutoff wavelength in the range of 346–363 nm and transmittance higher than 80% at 450 nm. They also exhibited high glass transition temperatures in the range of 310–343°C and the onset decomposition temperatures in the range of 435–462°C in nitrogen atmosphere. Meanwhile, these polyamide films possess good mechanical properties with tensile strengths of 76.4–86.1 MPa and elongations at break of 11.2%–27.3%. Due to those properties, these polyamides could be considered as photoelectric and microelectronic materials.

Based on the synthesis of a rigid aromatic diamine, α,α-bis(4-aminophenyl)-4-(t-butyl)toluene (1), a novel polyimide (PI) 3 was prepared from this diamine monomer and 4,4′-oxydiphthalic dianhydride via a one-step high-temperature polycondensation. FT-IR, ¹H NMR and elemental analysis were used to investigate the chemical structures of 1 and 3. The results confirmed that they agreed with the proposed structures for both 1 and 3 completely. The obtained PI 3 showed excellent solubility in most common solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, chloroform, dichloromethane and tetrahydrofuran. The resulting strong and flexible film exhibited high thermal stability with the glass transition temperature at 317°C and the temperature at 10% weight loss beyond 519°C in both air and nitrogen atmospheres. Moreover, the film also showed high optical transparency, low dielectric constant (3.13 at 1 MHz), low water absorption (0.40%) and hydrophobic character.

With in-situ bending various contents of nano-sized titanium dioxide (TiO₂) were introduced into the solution polymerization system of poly (p-phenylene benzobisoxazole) (PBO), and the blends were spun into high performance fibers via liquid crystal spinning. The dispersion of TiO₂ in matrix was observed by the scanning electron microscopy. The mechanical and thermal properties of PBO and TiO₂/PBO fibers were tested by a tensilon and a thermogravimetric analyser. The results show that the tensile strength and modulus of the PBO/TiO₂ fiber containing 1.5 wt % TiO₂ is 4.62 GPa and 109.99 GPa, which is approximately 36% and 18% higher than that of the pure PBO fiber. The decomposition temperature of the composites is also improved from 697.6°C to 701.8°C. The effect of TiO₂ nanoparticles on the structure of PBO is also studied. Copyright © 2009 John Wiley & Sons, Ltd.

A series of novel polyimides (PIs) (3a–d) were prepared from 3,3′,5,5′-tetramethyl-4,4′-diaminodiphenyl-4″-isopropyltoluene (1) with four aromatic dianhydrides via a one-step high temperature polycondensation procedure. The obtained PIs showed excellent solubility, with most of them dissoluble at a concentration of 10 wt % in amide polar solvents and chlorinated solvents. Their films were nearly colorless and exhibited high-optical transparency, with the UV cutoff wavelength in the range of 328–353 nm and the transparency at 450 nm >80%. They also showed low-dielectric constant (2.49–2.94 at 1 MHz) and low-water absorptions (0.44–0.65%). Moreover, these PIs possessed high-glass transition temperatures (T_g) beyond 327 °C and excellent thermal stability with 10% weight loss temperatures in the range of 530–555 °C in nitrogen atmosphere. In comparison with some fluorinated poly(ether imide)s derived from the trifluoromethyl-substituted bis(ether amine)s, the resultant PIs 3a–d showed better solubility, lower cutoff wavelength, and higher T_g. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3309–3317, 2009

Two kinds of modified poly(p-phenylene benzoxazole) (PBO), the copolymer of TPA (SPBO) and p-SPBO, containing ionic groups in the macromolecular chains were obtained by copolymerization from 1,3-diamino-4,6-dihydroxybenzene dihydrochloride (DAR) and terephthalic acid (TPA), with the addition of selected amounts (1.5–5.0% molar ratio over DAR) of 5-sulfoisophthalic acid monosodium salt or sulfoterephthalic acid monopotassium salt in place of the TPA, respectively, in poly(phosphoric acid) (PPA). The resultant PBO/PPA, SPBO/PPA, and p-SPBO/PPA lyotropic liquid-crystalline solutions were spun into fibers by a dry-jet wet-spinning technique. Chemically modified PBO fibers with sulfonate salt pendants in the polymer chains were obtained for the first time. The surface wetting behavior and interfacial shear strength between the fiber and epoxy resin were investigated. The interference of sulfonate salt pendants on the crystalline morphology was measured. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

A series of poly(ethylene-co-trimethylene terephthalate) (PETT) copolymers were prepared by polycondensation. The synthesized PETT are block copolymers and the content of poly(trimethylene terephthalate) (PTT) units incorporated into the copolymers are always larger than that fed in the polymerization. The nonisothermal crystallization at the different cooling rates was studied by means of differential scanning calorimetry. The copolymers develop the crystallization later and show the lower melting temperature than the corresponding enriched homopolymers. The modified Avrami analysis fit well the nonisothermal crystallization of these polymers. The overall rate of crystallization of PTT is fastest and that of PET is slowest, whereas the copolymers are between them at the same cooling rate. The minor PET units incorporated into PTT polymer chains reduce the crystallization of PTT segments, but the present minor PTT units in the PET chains seem to accelerate the crystallization of PET segments. The Avrami exponent nvaries in the range of 3–4, indicating that the nonisothermal crystallization follows the homogeneous nucleation and two- to three-dimensional growth mechanism. Wide angle X-ray diffraction analysis explains that the PET and PTT units do not cocrystallize and it is considered as the enriched polymer segments to crystallize during crystallization. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers