Rongjie Yang

Synthesis and characterization of thermally stable poly(urethane–imide)s based on novel diols-containing imide and alkynyl groups

Two novel diols having both imide and aromatic groups in main chains, including N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester glycol (PBDCG) and N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester butynediol (PBDCB), were synthesized. Then, the novel thermoplastic-segmented poly(urethane–imide)s (PUIs), in which 4,4′-diphenylmethane diisocyanate and the diols as the hard segments and poly(tetrahydrofuran) as the soft segments, were prepared via two-step polymerization. The prepared polymers were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel permeation chromatography, tensile tests and UL 94 vertical burn test. TGA result indicates that the novel PUIs with the rigid hard segments have slower degradation rates than the conventional polyurethanes, and PBDCB-based PUIs are more thermally stable than PBDCG-based PUIs. DSC and x-ray diffraction results confirm that they are amorphous structures. Moreover, DSC analysis indicates that the glass transition temperature of PUIs increases by increasing the contents of hard segments. The weight-average molecular weights of PUIs are in the range of 1.12–4.19 × 104. The UL 94 vertical burn test according to the ASTDM D3801 test method indicates that the PUIs are classified under vertical ranking V-2.

Organic/inorganic hybrid epoxy nanocomposites based on octa(aminophenyl)silsesquioxane

Octa(aminophenyl)silsesquioxane (OAPS) was used as the curing agent of diglycidyl ether of bisphenol-A (DGEBA) epoxy resin. A study on comparison of DGEBA/OAPS with DGEBA/4,4′-diaminodiphenyl sulfone (DDS) epoxy resins was achieved. Differential scanning calorimetry was used to investigate the curing reaction and its kinetics, and the glass transition of DGEBA/OAPS. Thermogravimetric analysis was used to investigate thermal decomposition of the two kinds of epoxy resins. The reactions between amino groups and epoxy groups were investigated using Fourier transform infrared spectroscopy. Scanning electron microscopy was used to observe morphology of the two epoxy resins. The results indicated that OAPS had very good compatibility with DGEBA in molecular level, and could form a transparent DGEBA/OAPS resin. The curing reaction of the DGEBA/OAPS prepolymer could occur under low temperatures compared with DGEBA/DDS. The DGEBA/OAPS resin didn’t exhibit glass transition, but the DGEBA/DDS did, which meant that the large cage structure of OAPS limited the motion of chains between the cross-linking points. Measurements of the contact angle indicated that the DGEBA/OAPS showed larger angles with water than the DGEBA/DDS resin. Thermogravimetric analysis indicated that the incorporation of OAPS into epoxy system resulted in low mass loss rate and high char yield, but its initial decomposition temperature seemed to be lowered.

Purity Analysis of Polyhedral Oligomeric Octa(nitrophenyl)silsesquioxane

The purity of polyhedral oligomeric octa(nitrophenyl)silsesquioxane (ONPS) was analyzed using high perform- ance liquid chromatography/ESI-Q-TOF MS (HPLC-ESI-Q-TOF MS). The peaks of ONPS and impurities could be distin- guished and the purity of ONPS could be calculated. The impurity peaks of HPLC were separated completely through changing the analytical conditions. The best HPLC conditions in the testing were obtained. The analytical time under these conditions was longer than under others. It was obtained that nitrophenylsilsesquioxane (NPS) was in 97.55 wt%. According to the analytical results from MS and the extracted ion chromatogram (EIC) HPLC-MS for ONPS, it could be found that in ONPS there is a little of nonanitro-octaphenylsilsesquioxane (9-NPS), but no 7-NPS and 10-NPS. It was supposed that ONPS and 9-NPS had the same ionization degree because of their very similar chemical structures. It was obtained that ONPS was in a purity of 92.42%, while the 9-NPS was in an amount of 5.13%, and impurities were in 2.45%. It was confirmed that nitro groups on the phenyl groups were at either para- or meta-position in ONPS according to the results of HPLC and the polarity analysis of different isomers. Compared to centrosymmetric structure of octaphenylsilsesquioxane (OPS), ONPS could be non-centrosymmetric due to difference of -NO2 substitution position on the phenyl groups. All of the possible polarity distri- butions were analyzed for the ONPS. It was pointed that there are seven kinds of different polarity distributions on ONPS molecules, and they are correspondent to the particular peaks of HPLC results, respectively. As well, the purity of ONPS was analyzed using ultra performance liquid chromatography (UPLC) and it provided consistent results with HPLC in high sepa- ration efficiency. It is suggested that the HPLC-ESI-Q-TOF MS method can be used to analyze the purity of ONPS. Keywords octa(nitrophenyl)silsesquioxane; purity analysis; HPLC-MS; UPLC