[An investigation of fast thermolysis of GAP/AP system by FTIR spectroscopy].

The rapid pyrolysis of GAP/AP system under simulated combustion conditions was investigated by an on-line analysis, i. e. so called T-Jump/FTIR. The results show that the compositions of the main gaseous products for pyrolysis are changed, in comparison with the pyrolyses of single, which indicates that the interactions occur between the components of GAP/AP system. From an obvious effect of pressure on the main gaseous products for GAP/AP pyrolysis it is shown that the interactions between GAP and AP components arise from the gaseous products of AP and both the reactions in gas phase and in gas/condensed phase occur in the GAP/AP mixed system. The interactions between GAP and AP are not affected by test temperature. It is considered that the real time analysis of gaseous products of energetic material pyrolysis under simulated combustion conditions would be carried out by T-Jump/FTIR on-line analysis technique and from microcosmic reaction a technical approach used to explore the rapid pyrolysis of energetic materials and interactions between their components at high temperature and pressure would be developed by the on-line analysis technique from microcosmic reaction.

Comparing the performance of FA, DFA and DMA using different synthetic long-range correlated time series.

Notwithstanding the significant efforts to develop estimators of long-range correlations (LRC) and to compare their performance, no clear consensus exists on what is the best method and under which conditions. In addition, synthetic tests suggest that the performance of LRC estimators varies when using different generators of LRC time series. Here, we compare the performances of four estimators [Fluctuation Analysis (FA), Detrended Fluctuation Analysis (DFA), Backward Detrending Moving Average (BDMA), and Centred Detrending Moving Average (CDMA)]. We use three different generators [Fractional Gaussian Noises, and two ways of generating Fractional Brownian Motions]. We find that CDMA has the best performance and DFA is only slightly worse in some situations, while FA performs the worst. In addition, CDMA and DFA are less sensitive to the scaling range than FA. Hence, CDMA and DFA remain "The Methods of Choice" in determining the Hurst index of time series.

[An investigation on fast thermolysis of ammonium perchlorate (AP) by FTIR spectroscopy].

The fast thermolysis processes of ammonium perchlorate (AP) and its chemical reaction mechanism under certain simulated conditions of combustion were systematically studied by means of T-Jump/FTIR technique. AP was flash-pyrolyzed under different pressure nitrogen atmosphere, with the heating rate of 1000 K x s(-1) and the set temperatures of 874 and 1 274 K. Thereafter, the real time species and concentration of its gaseous products were obtained and identified by using rapid scanning Fourier transform infrared (FTIR) in-situ spectroscopy. It was indicated that the main gaseous products of AP thermolysis is composed of NO2, N2O, NO, HCl and NClO. Interestingly, the values of N2O/NO2, NO/NO2 and NO/NClO are increased while the test temperature or pressure is elevated. It is suggested that the transformation of condensed phase and heterogeneous gas/condensed phase was probably arises and the "following reactions" among the main gaseous products may also take place in the fast thermolysis process of AP.

Preparation and characterization of poly(N-isopropylacrylamide)-modified poly(2-hydroxyethyl acrylate) hydrogels by interpenetrating polymer networks for sustained drug release.

In order to investigate the influence of hydrophobic moieties formed by poly(N-isopropylacrylamide) (PNIPAm) in a hydrogel matrix on the release behavior of the hydrogel, a series of poly(N-isopropylacrylamide) (PNIPAm)-modified poly(2-hydroxyethyl acrylate-co-2-hydroxyethyl 2-hydroxyethyl methacrylate) (P(HEA-co-HEMA)) via interpenetrating polymer networks (IPNs) were prepared by a sequential UV solution polymerization. Interestingly, it was found that P(HEA-co-HEMA)/PNIPAm IPN indicated a single glass transition temperature (T(g)) and the T(g)s of the IPNs increased with an increase in the PNIPAm component. This phenomenon may be attributed to hydrogen bonding between the two polymer networks, but the hydrogen bonding exerts less influence on the swelling behavior of the IPNs, due to the fact that IPNs can respond to changes in temperature like PNIPAm. Using 2-[(diphenylmethyl)sulphiny]acetamide (modafinil, MOD) and p-hydroxybenzoic acid (HBA) as model drug compounds, the release behavior of the IPNs was studied at body temperature, and it was found that the presence of PNIPAm could retard drug release regardless of the solubility of the drugs. Release profiles of HBA from the IPNs and their component samples as a function of time at 37 degrees C.

Preparation, properties and controlled release behaviors of pH-induced thermosensitive amphiphilic gels.

Two pH-induced thermosensitive amphiphilic gels for controlled drug release were constructed with thermosensitive poly(N-isopropylacrylamide) (PNIPAm) and hydrophobic poly(ethyl acrylate) (PEA) by interpenetrating polymer network (IPN) technology. To obtain pH-induced thermosensitive functionality at physiological temperature, 5 mol % of acrylic acid (AAc) and N, N-dimethyl aminoethyl methacrylate (DMA) were incorporated into PNIPAm chain by their copolymerization. It is found that the IPN hydrogels show pH-induced thermosensitivity at physiological temperature. When the amphiphilic gels with IPN structure were immersed in water, the hydrophobic moieties formed by PEA have the potential to act as reservoirs for hydrophobic drugs, from which drug may be released slowly. Using drug daidzein (DAI) as a model molecule, controlled release behaviors of the IPNs were investigated. It is found that the presence of permanently hydrophobic PEA network can indeed slow the release rate of DAI and to some extent overcome disadvantageous burst effect of PNIPAm-based networks in hydration state. The release kinetics of DAI from the IPNs seems to follow pseudo-zero-order release character, regardless of the hydrogels in swollen or shrunken state.