Aromatic poly(benzoxazole)s are a class of rigid-rod conjugated polymers. However, their poor solubility in organic solvents limits potential applications. Thus, a good method that can address this dilemma is needed, given that existing methods involve models with either poor solubility but good thermal stability or good solubility but poor thermal stability. In this paper we report a novel aromatic poly(benzoxazole) with a soft linkage and a rigid pendant group. Structural characterizations of the polymers via Fourier transform infrared and proton nuclear magnetic resonance spectroscopy reveal the formation of a benzoxazole ring and an imide ring. The introduction of rigid pendant groups improved the solubility and enhanced the thermal stability of the polymer, which was impaired by the incorporation of the soft linkage. Most of these polymers are soluble at room temperature or when heated in dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide. Some polymers can even be dissolved in m-cresol and tetrahydrofuran. A 10% weight loss in these polymers was observed at temperatures over 410 °C. Moreover, the incorporation of the imide pendant group increased the conjugation length of the polymer structural unit and accelerated electron delocalization. Copyright © 2012 Society of Chemical Industry

As a kind of rig-rod-like polymer, poly(p-phenylene benzobisoxazole) (PBO) has received great interest because of its excellent mechanical properties and good thermal stability. The use of PBO fibers, however, is limited due to its low sunlight stability. In this work, the photoaging of PBO fibers, as well as the effects of oxygen and moisture on their photoaging, is investigated by tensile strength measurements, infrared spectroscopy, molecular mass determination, and scanning electron microscopy. It is first time to find that the photoaging of PBO fibers includes two development stages. The physical aging is the dominate factor at the first stage of photoaging relative to the second stage, in which the chemical aging is the dominate factor. In the first degradation stage, long defects appear and develop parallel to the fiber axis. Little chemical change occurs in this stage. In the second degradation stage, the molecular mass of PBO decreases and chemical degradation occurs. Oxygen accelerates the occurrence of chemical degradation. It is also found PBO fibers are more stable for photoaging when moisture and oxygen are isolated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A novel benzoxazine monomer containing a benzoxazole group was synthesized using a nonsolvent method and then named DAROH-a. The structure of DAROH-a was confirmed by FTIR, ¹H NMR, elemental analysis, and mass spectrometry. The curing reaction activation energy was calculated at 140 kJ/mol. Its corresponding crosslinked polybenzoxazines, poly(DAROH-a), displayed a higher glass transition temperature at 402 °C, a 9% weight loss at the said temperature, and a high char yield of 42 wt % (800 °C, in nitrogen). Moreover, the dielectric constants of poly(DAROH-a) were low and changed only slightly at different temperatures. Furthermore, the dielectric constants and dielectric loss of poly(DAROH-a) at the same frequency barely changed from room temperature to 150 °C. The photophysical properties of poly(DAROH-a) film were also investigated. Poly(DAROH-a) showed an absorption peak at 280 nm. The photoluminescent emission spectrum of poly(DAROH-a) film displayed predominant emission peaks at 521 nm. It might have potential application as high-performance materials because of its excellent dielectric constants stability and thermal stability under high temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

A series of high-performance polymer/carbon nanotube (CNT) composites with different nanotube contents have been prepared via condensation of N-silylated diamino terminated precursor of the polymer with acid chloride-functionalized CNTs and subsequent thermal cyclodehydration. The composites have been fully characterized by infrared and Raman spectroscopy, electron microscopy, and thermal analysis. Various interesting morphologic features including helical structures have been observed in the composites as a result of covalent attachment of the polymer. The composites exhibit excellent thermal stability and a significant improvement in the dielectric constant and mechanical strength with the inclusion of CNTs. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Poly(p-phenylene benzobisoxazole) (PBO) fiber has received great interest because of its excellent mechanical properties and good thermal stability. The objective of this study was to expose degradation mechanism of PBO under neutral and acidic conditions by molecular mass and Fourier transform infrared (FTIR) spectroscopy. Results were not consistent with the classic degradation mechanism, which indicates that degradation should occur through the ring opening and chain scission of the benzoxazole ring. The FTIR absorption spectra of PBO suggested that the o-hydroxy amide linkage (the open ring structure) was present in the PBO molecule chain to some extent because of the incomplete polymerization. Further investigation showed that hydrolysis might occur in the open ring section during hydrolytic degradation. Based on the experimental data, a new degradation mechanism was proposed. It suggests that, in the early and middle stages, hydrolysis occurred primarily in the o-hydroxy amide linkage of the open ring. The concentration of the o-hydroxy amide structure determined the speed of degradation of PBO. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Polymer blend of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and poly(styrene-co-acrylonitrile) (SAN), which has broad commercial interest, has limited miscibility. A triblock terpolymer, polystyrene-block-polybutadiene-block-poly(methyl methacrylate) (SBM), is often used as compatibilizer to improve the miscibility of PPE/SAN. In this work, dissipative particle dynamics and molecular dynamics of Material Studio were used to study the essentials that influence miscibility of the blend systems, and then Flory–Huggins parameter χ, radial distribution function (RDF) and morphologies are analyzed. It shows that the blends with more content of styrene in SAN (above 90 wt%), whose mass percentage is 60%, are best miscible. For the systems of PPE/SAN added with SBM, the miscibility increases and then decreases with the increase of SBM content. A longer chain of styrene (S) in SBM leads to wrapped structure of PMMA by PB, wrapped by PS, resulting in decrease of the miscibility. From studies and simulation of χ and RDF, the best blend system for commercial and industrial use is the one with mass ratio of PPE/SAN/SBM 36/54/10, in which S content in SAN is above 90 wt%. For SBM, the ratio of chain length styrene (S)/butadiene (B) is lessthan 1, while B and M are the same in chain length. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

A novel perylene bisimide dye bearing carboxylphenylene substituents on the imide N atoms was synthesized and four conjugated copolymers containing different contents of perylene bisimide dye were synthesized via PPA/P₂O₅ copolymerization method. The structures of the four copolymers were characterized by FTIR, elementary analysis, ¹H-NMR and XRD. The copolymers showed good thermal stabilities but poor solubilities due to the high rigidity of the backbone. The photophysical characteristics of the copolymers were investigated by UV-Vis and PL spectra in solutions and films. Because of the conformational change of perylene bisimide chromophore, the absorptions of perylene bisimide core in copolymers showed a large blue-shift (56 nm) compared to that of the perylene monomer. In PL experiments, when exciting the benzoxazole, an obvious fluorescent quenching was observed in all copolymers, which can be attributed to the energy transfer from benzoxazole units to perylene bisimide fragments and fluorescence quenching. With increasing perylene content, the copolymers turned to layered and friable. The XRD test showed that the interchain distances increased slightly with increasing perylene content. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

In this study, the shear flow properties of Poly(p-phenylene benzobisoxazole) (PBO)/poly(phosphoric acid) (PPA) spinning dope were studied by means of capillary rheometer. The effect of shear stress, temperature, PBO concentration, and PBO molecular weight on the apparent viscosity of PBO/PPA dope was discussed. The results showed that the apparent viscosity of the dope decreased with the increase of the shear stress and the temperature. The flow behavior index increased with the increase of temperature, which indicated that the non-Newtonian behavior of the dope became weaker at high temperature. Moreover, it was also found that at high shear stress, the apparent viscosity of the dope was insensitive to the temperature, PBO molecular weight, and PBO concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008