The straightforward self-assembly reaction of R3Sn+ and [Fe(CN)6]3? affords three-dimensional (3-D) coordination polymers [(n-Bu3Sn)2(R3Sn)Fe(CN)6]n, R = n-Bu(I) or Ph(II). The architecture of these coordination polymers is closely related to zeolite and acts as a host with wide internal cavities or channels capable of encapsulating voluminous organic compounds. Aniline derivatives acting as guest are encapsulated within the cavities of the 3-D-polymeric hosts I and II by tribochemical reaction producing host–guest supramolecular polymers. The structures and physical properties of these hosts and their host–guest systems were investigated by elemental analysis, X-ray powder diffraction, IR, UV-vis, EPR, and magnetic measurements. The morphology of these systems was examined by scanning electron microscopy (SEM). The interesting feature of these host–guest supramolecular polymers is the enhanced electrical conductivities over those of the 3-D-coordination polymeric hosts upon encapsulation of conductive polymers within their cavities. 相似文献
High-temperature polymerization of ?-caprolactam by using the salts derived from MAlEt4 (where M is Li, Na, and K) and monomer as catalyst was carried out. Polymerization occurs at 140–170°C, a temperature at which alkali metal caprolactamate has almost no catalytic activity for initiation. m-Cresol-insoluble polymer was obtained at temperatures lower than 231°C. Formation of a m-cresol-insoluble polymer depends on the polymerization temperature and time, and was observed under conditions where Al(Lac)3 has no catalytic activity. All the polymers obtained by NaAl(Lac)4–n(NHBu)n (n = 1 or 2) at 202°C were soluble in m-cresol. These trends observed in the case of MAl(Lac)4 are considered to be due to initiation by Al(Lac)3, which is a component of the catalyst used. 相似文献
Summary: The effective immobilization and activation of a single‐site chromium catalyst for ethylene polymerization has been achieved using MgCl2/AlRn(OEt)3 − n supports, without the use of methylaluminoxane (MAO) or a borate activator. High catalyst activity and a spherical polyethylene‐particle morphology is obtained. Furthermore, the single‐site characteristics of the catalyst are retained, the narrow molecular weight distribution of the polymers obtained are apparent from gel permeation chromatography (GPC) and confirmed by rheological characterization.
Shear frequency dependence of the storage modulus of (♦ and ▴) polyethylene ( = 1.8–1.9) prepared using an immobilized Cr catalyst, compared to (▪) a reference polymer having = 4.1. 相似文献
Enzyme-catalyzed preparation of polymers offers several potentially valuable advantages over the usual polymerization procedures. (1) Such polymerizations may allow the polymer to retain functionality that would be destroyed under normal polymerization conditions. (2) The selectivity provided by enzyme catalysts may permit polymers, including optically active polymers, to be prepared that are either not accessible or accessible only with difficulty by other methods. (3) The characteristics of the enzyme and the mild polymerization conditions may permit formation of polymers having highly regular sizes and backbone structures. This report describes the first successful use of an enzyme-catalyzed polycondensation to prepare a chiral (AA–BB)x polyesters of more than a few repeat units. Polymerization of bis(2,2,2-trichloroethyl) alkanedioates (BB) with diols (AA) using the enzyme porcine pancreatic lipase (PPL) as a catalyst is detailed. The polycondensations were carried out at ambient temperature in anhydrous, low polarity organic solvents such as ether, THF, and methylene chloride. End group analysis by NMR provided Mn values of 1300–8200 daltons while GPC provided Mw values of 2800–14900 daltons for the polymers. Based on proton NMR spectra obtained during the polymerization, relatively rapid formation of an AA–BB “dimer” and an AA–BB–AA “trimer,” slower formation of a BB–AA–BB “trimer,” and subsequent condensation of these to give higher polymers are suggested to be components of the polymerization mechanism. 相似文献
Twelve amphiphilic polymers were synthesized using poly(ethylene glycols) (PEGs) of different molecular weights, viz. 1000, 2000 and 4000 as hydrophilic block and linkers namely azelaic acid, sebacic acid, dimethyl isophthalate acid and dimethyl terephthalate as hydrophobic block in the presence of catalyst Conc. H2SO4. Synthesized polymers were characterized by using 1H-NMR, 13C-NMR and IR spectroscopy. Micellar sizes of the polymers were determined using Dynamic Light Scattering (DLS) which ranged from 51.6–174 nm for aliphatic polymers and 135.5–371 nm for aromatic polymers. Transmission Electron Microscope (TEM) results confirm the findings of DLS. Critical Micelle Concentrations (CMC) of the synthesized polymers were determined using electrical conductivity meter which ranged from 95 to 130 mg L?1 for aliphatic polymers and 420–1500 mg L?1 for aromatic polymers. 相似文献
Polymerization of butadiene sulfone (BdSO2) by various catalysts was studied. Azobisisobutyronitrile (AIBN), butyllithium, tri-n-butylborn (n-Bu)3B, boron trifluoride etherate, Ziegler catalyst, and γ-radiation were used as catalysts. Butadiene sulfone did not polymerize with these catalysts at low temperatures (below 60°C.), but polymers were obtained at high temperature with AIBN or (n-Bu)3B. The polymerization of BdSO2 initiated by AIBN in benzene at 80–140°C. was studied in detail. The obtained polymers were white, rubberlike materials and insoluble in organic solvents. The polymer composition was independent of monomer and initiator concentrations and reaction time. The sulfur content in polymer decreased with increasing polymerization temperature. The polymers prepared at 80 and 140°C. have the compositions (C4H6)1.55- (SO2) and (C4H6)3.14(SO2), respectively, and have double bonds. These polymers were not alternating copolymers of butadiene with sulfur dioxide. The polymerization mechanism was discussed from polymerization rate, polymer composition, and decomposition rate of BdSO2. From these results, the polymerization was thought to be “decomposition polymerization,” i.e., butadiene and sulfur dioxide, formed by the thermal decomposition of BdSO2, copolymerized. 相似文献
Polymerization of vinyl chloride by the ternary catalyst system of VOCl3–AIRnCl3–n complexing agent was investigated. It was suggested that the formation of a polar complex (or charge-transfer complex) between AlRnCl3–n and the complexing agent participated in the polymerization of vinyl chloride. In the copolymerization of vinyl chloride with propylene with the present catalyst system, it was more difficult to incorporate the propylene unit in the copolymer than with a typical radical catalyst. 相似文献