纳米材料的应用及新进展

介绍了纳米粒子的优异特性。着重介绍了聚合物／无机纳米粒子复合材料的主要制备方法，研究现状及应用和2000年聚合物粘土纳米复合材料的最新进展。     

Organic–inorganic polyimide nanocomposites containing a tetrafunctional polyhedral oligomeric silsesquioxane amine: synthesis,morphology and thermomechanical properties

5,11,14,17‐Tetraanilinooctaphenyl double decker silsesquioxane, a well‐defined tetraamino polyhedral oligomeric silsesquioxane (POSS), was synthesized in this work. This novel tetrafunctional POSS amine was employed to prepare polyimide nanocomposites. It was found that the hybrid polyimide nanocomposites displayed nanostructures in which the POSS component was aggregated into spherical microdomains with a diameter of 40 ? 80 nm. Compared to unmodified polyimide, the POSS‐containing polyimide nanocomposites displayed improved thermal stability and surface hydrophobicity. Owing to the introduction of the POSS microdomains, the dielectric constants of the polyimide nanocomposites were significantly decreased in comparison with plain polyimide. © 2017 Society of Chemical Industry     

Detecting structural orientation in isoprene rubber/multiwall carbon nanotube nanocomposites at different scales during uniaxial deformation

Enhanced strain‐induced crystallization (SIC) behavior in isoprene rubber/multiwall carbon nanotube (IR/MWCNT) nanocomposites was analyzed in terms of structural orientation during uniaxial deformation. In situ synchrotron wide‐angle X‐ray diffraction and small‐angle X‐ray scattering (SAXS) reveal the molecular orientation in IR/MWCNT composites at different scales. The inclusion of MWCNTs leads to a decrease in the molecular orientation at small strain due to the promotion of SIC. Meanwhile, the presence of MWCNTs induces a large‐scale orientation within the vulcanized rubber network based on SAXS results. Considering the heterogeneous nature of the vulcanized network, the nucleation process during SIC is discussed from the viewpoint of thermodynamics. The oriented large‐scale structure in IR/MWCNT composites is composed of local rubber chains stretched up MWCNTs, from which the additional nuclei are induced. By forming a bound rubber layer around MWCNTs through attractive interactions, MWCNTs can amplify the local strain of rubber segments and form a highly oriented large‐scale structure, but without altering the overall molecular orientation level. The evolution of detailed structural orientation in MWCNT‐filled rubber composites during deformation is revealed for the first time. © 2017 Society of Chemical Industry     

Synthesis and antimicrobial activity of biocidal polymer–montmorillonite nanocomposites

The bioactive agents p‐hydroxymethylbenzoate, 2,4‐dihydroxymethylbenzoate and methylsalicylate were reacted with polyoxyalkylene (D_230–2000)–montmorillonite (MMT) intercalated nanocomposites. D_230–2000–MMT were prepared by an ion exchange process of Na‐MMT and? NH₃⁺ groups in polyoxyalkylene amine hydrochloride of three different molecular masses (D₂₃₀, D₄₀₀ and D₂₀₀₀). The results of X‐ray analysis and transmission electron microscopy show that D₂₀₀₀–MMT/p‐hydroxymethylbenzoate is an exfoliated nanocomposite, whereas in D₂₃₀–MMT/p‐hydroxymethylbenzoate, D₂₃₀–MMT/2,4‐dihydroxymethylbenzoate, D₂₃₀–MMT/methylsalicylate and D₄₀₀–MMT/p‐hydroxymethylbenzoate, having lower molecular mass and polymer loading, the MMT rearranges in an intercalated and flocculated structure. The amount of intercalated polymer and interaction between polymer and layered silicate were determined using thermogravimetric analysis and Infrared spectroscopy. The antimicrobial activities of the nanocomposites were qualitatively and quantitatively assessed by agar diffusion tests and minimal inhibitory concentration values against a Gram‐negative bacterium (Escherichia coli NCIM 2065), a Gram‐positive bacterium (Bacillus subtilis ATCC) and fungi (Candida albicans SC5314 and Cryptococcus neoformans). The D₂₀₀₀–MMT/p‐hydroxymethylbenzoate nanocomposite strongly inhibits the growth of all the micro‐organisms tested. The diameter of the inhibition zone varies according to the type of micro‐organism tested. The effect of nanocomposite concentration on morphology, respiration and release of calcium, potassium and sodium ions of the test micro‐organisms was examined. Copyright © 2011 Society of Chemical Industry     

A facile route to develop electrical conductivity with minimum possible multi‐wall carbon nanotube (MWCNT) loading in poly(methyl methacrylate)/MWCNT nanocomposites

Today, we stand at the threshold of exploring carbon nanotube (CNT) based conducting polymer nanocomposites as a new paradigm for the next generation multifunctional materials. However, irrespective of the reported methods of composite preparation, the use of CNTs in most polymer matrices to date has been limited by challenges in processing and insufficient dispersability of CNTs without chemical functionalization. Thus, development of an industrially feasible process for preparation of polymer/CNT conducting nanocomposites at very low CNT loading is essential prior to the commercialization of polymer/CNT nanocomposites. Here, we demonstrate a process technology that involves in situ bulk polymerization of methyl methacrylate monomer in the presence of multi‐wall carbon nanotubes (MWCNTs) and commercial poly(methyl methacrylate) (PMMA) beads, for the preparation of PMMA/MWCNT conducting nanocomposites with significantly lower (0.12 wt% MWCNT) percolation threshold than ever reported with unmodified commercial CNTs of similar qualities. Thus, a conductivity of 4.71 × 10^?5 and 2.04 × 10^?3 S cm^?1 was achieved in the PMMA/MWCNT nanocomposites through a homogeneous dispersion of 0.2 and 0.4 wt% CNT, respectively, selectively in the in situ polymerized PMMA region by using 70 wt% PMMA beads during the polymerization. At a constant CNT loading, the conductivity of the composites was increased with increasing weight percentage of PMMA beads, indicating the formation of a more continuous network structure of the CNTs in the PMMA matrix. Scanning and transmission electron microscopy studies revealed the dispersion of MWCNTs selectively in the in situ polymerized PMMA phase of the nanocomposites. Copyright © 2012 Society of Chemical Industry     

A different approach for the study of the crystallization kinetics in polymers. Key study: poly(ethylene terephthalate)/ SiO2 nanocomposites

Polymer crystallization is complex and difficult to model, especially when it is non‐isothermal and even more so when describing cold crystallization. In most cases, two different processes occur, so‐called primary and secondary crystallization. In the literature, two assumptions are generally made. Firstly, the validity of the Avrami model is assumed a priori. Secondly, for calculations of the kinetic parameters and activation energy, data from a single differential scanning calorimetry scan at a given heating rate are used. The other popular model, that of Ozawa, is also based on similar assumptions. In the study reported here, a different approach was adopted, which uses multiple scans at various heating rates simultaneously. Here the experimental data of the non‐isothermal cold crystallization of an in situ‐prepared poly(ethylene terephthalate)/1% SiO₂ nanocomposite were used. Data were analysed following both the ordinary procedure and the method proposed in this work. Findings showed that when the Avrami model is a priori supposed to hold and the data of different heating rates are analysed separately, results are not acceptable. The new approach involves calculation of the activation energy through use of the isoconversional methods of Ozawa–Flynn–Wall and Friedman over the whole range of the crystallization conversion. The reaction model f(a) was determined after the evaluation of 16 different models. The best fitting was achieved for the Prout–Tompkins model or for a mechanism involving two steps described by respective Avrami equations with different activation energies. Copyright © 2010 Society of Chemical Industry     

Physical properties and morphology of films prepared from microfibrillated cellulose and microfibrillated cellulose in combination with amylopectin

Two types of microfibrillated cellulose (MFC) were prepared using either a sulfite pulp containing a high amount of hemicellulose (MFC 1) or a carboxymethylated dissolving pulp (MFC 2). MFC gels were then combined with amylopectin solutions to produce solvent‐cast MFC‐reinforced amylopectin films. Tensile testing revealed that MFC 2‐reinforced films exhibited a more ductile behavior and that MFC 1‐reinforced films had higher modulus of elasticity (E‐modulus) at MFC loadings of 50 wt % or higher. Pure MFC films had relatively low oxygen permeability values when data were compared with those for a variety of other polymer films. MFC 1 and MFC 2 films had similar opacity but differences in appearance which were attributed to the presence of some larger fibers and nanofiber agglomerates in MFC 2. Field emission scanning electron microscopy (FE‐SEM) and atomic force microscopy (AFM) were used to illustrate the morphology of MFC nanofibers in pure films and in an amylopectin matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Formation of highly oriented biodegradable polybutylene succinate adipate nanocomposites: Effects of cation structures on morphology,free volume,and properties

Many biodegradable polymer materials have not been found to be suitable replacements for more traditional non‐biodegradable polymers owing to their insufficient gas and vapor barrier properties. The use of a series of novel organically modified synthetic fluorohectorites (FHTs) has been explored to produce biodegradable polybutylene succinate adipate (PBSA)‐clay nanocomposites with improved barrier. Highly oriented nanoclay structures (clearly showing a tortuous path required to reduce gas and vapor transmission) were observed using transmission electron microscopy (TEM), resulting in a significant reduction in oxygen permeability (up to a 53% decrease). In particular, these oriented structures were observed in the FHTs modified with di poly(oxyethylene) alkyl methyl ammonium and the longer chain dimethyl dialkyl ammonium. Orientation and dispersion were found to be a result of chemical functionality, chain length, and unique aspect ratios of these FHTs. It was concluded that this reduction in permeability was predominantly due to the tortuous path created by oriented platelets and not from any nucleating effects the platelets may have had. Interestingly, the FHTs were shown to disrupt crystallinity and no change in free volume (as measured using positron annihilation life‐time spectroscopy) was observed. The excellent clay dispersion and orientation also led to significant increases in other properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Reinforcement and antioxidation effects of fullerenol‐containing natural rubber

Natural rubber (NR) containing fullerenol, C60‐OH, was prepared by two methods; one by mixing C60‐OH aqueous solution to NR latex followed by coagulation (wet method) and the other by mixing C60‐OH powder with solid rubber by an open roll mixer (dry method). C60‐OH mixed by wet method was homogeneously dispersed in the rubber, while one mixed by dry method was particles in the size up to 70 μm. The former exhibited large reinforcing and antiaging effect than the latter. The large antiaging effect was explained by the finding that C60‐OH had large radical scavenging ability and gel forming ability during heat treatment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Conversion and shrinkage analysis of acrylated hyperbranched polymer nanocomposites

The photo‐curing behavior of composites containing nanosized SiO₂ in an acrylated hyperbranched polymer matrix was investigated by means of photo differential scanning calorimetry. The chemical conversion data were analyzed using an autocatalytic model, paying close attention to the influence of composition and UV intensity. It was shown that the reaction order and the autocatalytic exponent were independent of UV intensity and filler fraction, whereas the rate constant showed strong intensity dependence, but weak filler dependence. Maximum conversion was independent of UV intensity, but was reduced when a filler was present. The dispersion state influenced the gel‐point of the composites, but had no influence on the overall cure kinetics. Cure shrinkage reduction of ～ 33% could be achieved by adding 20 vol% of filler. This was attributed to the reduced double bond conversion of the matrix due to the presence of the filler. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009