Volume 18, Issue 5

For the past decade, market demands for semicrystalline heat-resistant polyamides (HPAs) with excellent performance and significantly improved heat-resistant temperature has grown rapidly, and they are widely used in the electronic and electrical industry, as light-emitting diodes and in the automobile field (as metal replacements). Industrialized HPAs to date, include PA46, PA6T copolyamides, PA9T and PA10T. Other HPAs being researched include full aliphatic HPA, PA5T, long carbon chain HPA, PXD10 and alicyclic HPA. This review addresses progress in HPAs, especially the properties of HPA, patents analysis and polymerization processes.

A new functional pH-responsive polyurethane-based nanomicelle has been developed with BES-Na as the functional monomer, the buffering agent with tertiary amine, and sulfonic acid group was incorporated into the hydrophilic shell as the functional agent, which resulted in polyurethane nanosystem with pH-sensitive property. Folic acid (FA) was chosen as model hydrophobic drug to evaluate the loading and pH-triggered release of the PU micelles in vitro drug loading and release. The drug loading content (LC) and the encapsulation efficiency (EE) for FA-loaded micelles in phosphate-buffered solutions were 7.68% and 27.72%, respectively, and the largest accumulative drug release percentages in pH 6.8 and pH 5.0 were 79.17% and 89.83% in 24 h, respectively. A facile and versatile approach has been provided for the design and fabrication of smart nanovehicles for effective drug delivery and opens a new thought in the design and fabrication of biodegradable polyurethanes for next generation of nanomicellar systems.

While in molar mass determinations different averages are clearly distinguished, such differentiation is usually not performed when dealing with the composition of copolymers or polymer blends. The present article shows that the mol ratio calculated by nuclear magnetic resonance (NMR) usually provides neither a weight nor a number average. Only if the composition does not vary with molar mass, or if both copolymer units are of equal molar mass, a weight average mol ratio is obtained from NMR measurements. The frequent assumption that NMR yields a number average composition is incorrect, therefore. However, the mass fraction calculated from NMR corresponds to the weight average mass fraction.

Poly(isobutylene -co-p -methylstyrene) (IB/ p -MeSt) random copolymer is a new generation of polyisobutylene-based elastomer. The cationic copolymerization of IB with p -MeSt was thoroughly examined by using various initiating systems in [Hmim][NTf 2 ] at −30°C. The effects of initiating systems and monomer feed ratio on the monomer conversion, molecular weight and copolymer composition are discussed. The polymers were characterized by 1 H-nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy and matrix-assisted laser desorption/ionization-time-of-flight-mass spectroscopy (MALDI-TOF-MS) to determine their chemical composition and molecular structure. The results show that high polarity, high viscosity and ionic environment of ionic liquids (ILs) influenced the copolymerization. The corresponding mechanism of cationic copolymerization in ILs is also proposed.

This study aimed to improve the flexibility of E-51 epoxy resin by using polyamide/polyether amine as a two-component curing agent. Through solid state nuclear magnetic resonance (SSNMR), it was found that the cross-linking density of epoxy resin could be effectively reduced by adding the polyamide and polyether amine curing agent. The tensile tests showed that the elongation-at-break was remarkably improved. It was found by differential scanning calorimetry (DSC) that the curing behavior of the polyamide epoxy curing system varied with the addition of different polyether amine. Phase contrast microscope showed that phase separation occurred during the reaction of epoxy resin with the polyamide/polyether amine composite curing agent. In this paper, the modified epoxy resin was endowed with high elongation-at-break (>100%) and appropriate tensile strength (10~20 MPa).

Conventional glass fiber/unsaturated polyester resin (UPR) composites were fabricated by four layers to verify the optimum fabrication conditions such as the initial curing temperature, fiber changes and vacuum. Before that another optimum condition for stir mixing multi-walled carbon nanotubes (MWCNTs) into UPR was further investigated based on the initial curing temperature. Exothermic temperature measurements, density measurements, thermo-gravimetric analysis and tensile testing were utilized to identify the effects of these factors on the UPR and composite laminates. Consequently, an initial curing temperature range of 25°C–35°C was recommended to start the polymerization. In addition, the fiber combination and applying vacuum were also represented as the other optimum conditions in composite fabrication. The optimum initial curing temperature was applied for modifying UPR with 0.1 wt.% MWCNTs. Then, all of optimum conditions were used to fabricate glass fibers/modified UPR composites. The higher tensile strength and modulus of fiber combination with the adding of MWCNTs were obtained at 25.29 MPa and 1.39 GPa, respectively. The results indicate that simple MWCNT mixing can be used in industry due to the reduction of the fabrication time and better tensile properties.

Two novel poly(pyridinylene vinylene) (PPV)-type conjugated polyelectrolytes 2,6-PPYPV-(2+) and 3,5-PPYPV-(2+) were synthesized via Heck coupling reaction and characterized by 1 H nuclear magnetic resonance (NMR), ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. The two polymers consisting of meta-position substituted pyridinylenes as the metal recognition unit and a water-soluble divinyl-benzene derivative in the backbones. 2,6-PPYPV-(2+) and 3,5-PPYPV-(2+) both exhibit strongest fluorescence in methanol and weakest fluorescence in water among common polar solvents. In respect of ion detection, 3,5-PPYPV-(2+) has an excellent identifiability for Pd 2+ in methanol with the K_SV value of 1.1×10 5 m −1 while 2,6-PPYPV-(2+) has a good selectivity for Cu 2+ and Hg 2+ in aqueous solution. And all the Stern-Volmer plots of 2,6-PPYPV-(2+) and 3,5-PPYPV-(2+) in fluorescence quenching for metal ions have favorable tendencies. All the results suggest that 2,6-PPYPV-(2+) and 3,5-PPYPV-(2+) are promising materials in the applications of high performance chemosensors for some specific metal ions.