Variation of the mechanical and thermal characteristics of poly(4,4′-oxydiphenylenepyromellitimide) and poly{1,3-bis(3′,4-dicarboxyphenoxy)benzene [4,4′-bis)4′-N-phenoxydiphenylsulfone]imide} films and nanocomposites based on these polyimides and filled by carbon nanocones/disks in the course of hydrolysis in an alkaline solutions was studied. The goal of the study was to obtain systematic information about the influence exerted by carbon nanoparticles introduced into polyimide films with varied chemical structure on the stability of the resulting film materials against a prolonged action of active hydrolyzing media. It was shown that the hydrolytic stability of the materials under study is largely determined by the molecular packing density. Introduction of nanoparticles into the polymers under study may result in that the concentration in the material of the excess free volume localized at polymer–filler interfaces increases. This, in turn, causes a decrease in the hydrolytic stability of the nanocomposite film as compared with unfilled films of the matrix polyimide. The opportunity was considered of raising the hydrolytic stability of the polyimide and nanocomposite material by making higher the average packing density. 相似文献
Conducting materials based on polypyrrole-modified nanofibers of polylactides of different molecular masses and copolymers of ε-caprolactam (–NH–(CH2)5–CO–) and hexamethylenediamine adipate (–H(CH2)6NHCO(CH2)4CO–) were prepared. As shown by scanning electron microscopy, oxidative polymerization of pyrrole on the polymer nanofiber matrix depends on the nanofib er hydrophilicity. The heterophase synthesis of polypyrrole on the surface of hydrophilic nanofibers of the aliphatic copolyamide allowed uniform coating of the material surface with polypyrrole nanoparticles. The surface resistivity of the composite material was about 0.4 kΩ sq–1. 相似文献
Aromatic polyimides are well known as high performance polymers owing to their excellent thermal stability, mechanical and electrical properties1,2. In the preparation of polyimides, aromatic dianhydride monomer plays a critical role3. Although aromatic t… 相似文献
Alginate, a natural polysaccharide that has shown great potential as a cell scaffold for the regeneration of many tissues, has only been nominally explored as an electrospun biomaterial due to cytotoxic chemicals that have typically been used during nanofiber formation and crosslinking. Alginate cannot be electrospun by itself and is often co‐spun with poly(ethylene oxide) (PEO). In this work, a cell adhesive peptide (GRGDSP) modified alginate (RA) and unmodified alginate (UA) were blended with PEO at different concentrations and blending ratios, and then electrospun to prepare uniform nanofibers. The ability of electrospun RA scaffolds to support human dermal fibroblast cell attachment, spreading, and subsequent proliferation was greatly enhanced on the adhesion ligand‐modified nanofibers, demonstrating the promise of this electrospun polysaccharide material with defined nanoscale architecture and cell adhesive properties for tissue regeneration applications.
Aromatic polyimides are widely used in the microelectronic industry as electrical insulators, passivation layers, and liquid-crystal alignment layers, because of their excellent mechanical, electrical, chemical, and thermal properties1,2. Despite their ou… 相似文献
The deoxygenation reaction of heptanones, cycloheptanone, cycloheptatrienone or substituted cycloheptatrienone with dihalo-carbene results in carbon monoxide and corresponding halides. The yield of CO produced by 2 , 4 , 6-triphenylcycloheptatrienone is 2.6-3.5 times as high as that produced by the saturated heptanones. The structures, energies, charge distributions, bond orders, and other relative parameters of the dihalocarbonyl glides were calculated by using the SCF-MNDO method. The obtained data reveal that the ylides from cycloheptatrienone have aromatic structure and are different from those produced from saturated cycloheptanone. The reactivities of the dihalocarbonyl ylides are discussed. It is proposed that this aromatic structure should be responsible for the high yield of CO from the reaction of cycloheptatrienone with dihalocarbene. 相似文献
Russian Journal of Physical Chemistry A - SrTiO3 nanofibers were fabricated by an electrospinning process. The phase, microstructure and photocatalytic activity of the obtained SrTiO3 nanofibers... 相似文献
