The number and weight chemical composition distributions in random terpolymers were derived using a statistical approach. The solution was then generalized to comprise higher multicomponent copolymers. The analytical solution was verified with Monte Carlo simulations and by considering limiting cases. Chemical composition distributions for fractions of random terpolymers of various kinetic chain lengths were also investigated. In a similar way to the results for binary copolymers described by Stockmayer's distribution, broadening of the distribution is observed for low‐molecular‐weight chains.
Comparison of chemical composition distributions from Stockmayer (Equation ( 3 )) and statistical approach (Equation ( 4 )). 相似文献
A sensitive, simple, fast, and inexpensive method for determining diuron in water using square wave voltammetry and a glassy carbon electrode is presented. This method was developed to evaluate diuron contamination in river waters close to sugarcane cultivation, located in the metropolitan region of João Pessoa, in the state of Paraíba, Brazil. An analytical curve with a linear response ranging from 38.5–115.0 nmol L−1 (r2 = 0.993), a LOD equal 0.2 nmol L−1, and recovery rates from 88.0 to 108.0 %. The proposed method does not require any previous chemical treatment of the sample, thus contributing to green analytical chemistry. 相似文献
Undivided electrochemical cells enable economical preparation of sulphur-containing naphthoquinones through electrochemical sulphenylation of quinoidal compounds. The environmentally friendly and efficient protocol eliminates the use of chemical oxidants and facilitates the synthesis of the desired molecules. This approach offers an efficient and versatile method to synthesize quinones that exhibit cytotoxicity against cancer cell lines. 相似文献
Ethylene-propylene-diene rubber (EPDM) was reacted with thioacetic acid in the presence of 2,2′-azoisobutyronitrile (AIBN), giving rise to thioacetate-modified EPDM (EPDMTA). The extent of the incorporation was studied as a function of both thioacetic acid and AIBN concentration and reaction time. The products were analyzed by FTIR spectroscopy, sulfur content, and 1H NMR spectroscopy. The hydrolysis of EPDMTA in a NaOH methanolic solution resulted in mercapto-modified EPDM (EPDMSH). The addition of 5 wt.-% of this functionalized copolymer to a sulfur-vulcanized nitrile rubber (NBR)/EPDM (70 : 30 wt.-%) blend accelerated the vulcanization process as indicated by oscillating disk rheometer analysis. In addition, an improvement of mechanical and ageing properties was also observed. 相似文献
We refine the affine classification of real nets of quadrics in order to obtain generic curvature loci of regular 3-manifolds in and singular corank one 3-manifolds in . For this, we characterize the type of the curvature locus by the number and type of solutions of a system of equations given by four ternary cubics (which is a determinantal variety in some cases). We also study how singularities of the curvature locus of a regular 3-manifold can go to infinity when the manifold is projected orthogonally in a tangent direction. 相似文献
The formation of long‐chain branches (LCBs) during ethylene polymerization with a combination of catalysts was studied by Monte Carlo simulation. The model describes polymerization with a non‐branching catalyst that produces linear macromonomers, and a branching catalyst that produces linear and branched macromonomers. The LCBs are formed when the branching catalyst incorporates a macromonomer. The discussion is based on the three types of chain topology obtained during the synthesis: linear, comb‐branched, or hyperbranched. Simulation results show how the chain length distribution and the number of LCBs change according to the ratio between the two catalysts present in the reactor. The ratio hyperbranched/comb‐branched is defined to evaluate the system composition and the contribution of each catalyst. 相似文献
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
Whether tetra-tert-butyl-s-indacene is a symmetric D2h structure or a bond-alternating C2h structure remains a standing puzzle. Close agreement between experimental and computed proton chemical shifts based on minima structures optimized at the M06-2X, ωB97X-D, and M11 levels confirm a bond-localized C2h symmetry, which is consistent with the expected strong antiaromaticity of TtB-s-indacene. 相似文献