Summary: We present results for the temperature and pressure dependence of local structure and chain packing in cis‐1,4‐polybutadiene (cis‐1,4‐PB) from detailed molecular dynamics (MD) simulations with a united‐atom model. The simulations have been executed in the NPT statistical ensemble with a parallel, multiple time step MD algorithm, which allowed us to access simulation times up to 1 µs. Because of this, a 32 chain C128cis‐1,4‐PB system was successfully simulated over a wide range of temperature (from 430 to 195 K) and pressure (from 1 atm to 3 kbar) conditions. Simulation predictions are reported for the temperature and pressure dependence of the: (a) density; (b) chain characteristic ratio, Cn; (c) intermolecular pair distribution function, g(r), static structure factor, S(q), and first peak position, Qmax, in the S(q) pattern; (d) free volume around each monomer unit along a chain for the simulated polymer system. These were thoroughly compared against available experimental data. One of the most important findings of this work is that the component of the S(q) vs. q plot representing intramolecular contributions in a fully deuterated cis‐1,4‐PB sample exhibits a monotonic decrease with q which remains completely unaffected by the pressure. In contrast, the intermolecular contribution exhibits a distinct peak (at around 1.4 Å−1) whose position shifts towards higher q values as the pressure is raised, accompanied by a decrease in its intensity.
3D view of the simulation box containing 32 chains of C128cis‐1,4‐polybutadiene at density ρ = 0.849 g · cm−3 and the conformation of a single C128cis‐1,4‐PB chain fully unwrapped in space. 相似文献
1,2-Polybutadiene-block-poly(ethylene oxide)s were prepared by anionic polymerization and were subsequently modified by radical addition of ω-functional mercaptans (functional groups: carboxylic acid, amine, ethylene glycol, and fluorocarbon). The degree of functionalization of the products at full conversion of double bonds is 60–80%, and the molecular weight distribution is as narrow as that of the precursor polymer. The modified block copolymers are amphiphilic in nature and form complex aggregates in dilute aqueous solution. 相似文献
Chemical communication between macromolecules was studied by observing the controlled single chain collapse that ensues the exchange of a metal cross-linker between two polymer chains. The rhodium (I) organometallic cross-linker transfer from a low molecular weight collapsed polybutadiene to a larger polymer was followed using size exclusion chromatography. The increased effective molarity in the larger polymer seems to be the driving force for the metal migration. Thus, we demonstrate here a strategy for transferring a molecular signal that induces chain collapse of a polymer chain based on non-covalent interactions, mimicking biological behaviors reminiscent of signal transductions in proteins. 相似文献
This paper shows that the stiffness of styrene-butadiene solid rubber with added kaolin powder is related to the yield stress of kaolin dispersion in liquid polybutadiene rubber up to the percolation threshold.For five kinds of kaolin powder,the value of τ spans the range of 100-430Pa,while the corresponding compressive elastic constant of SBR varies from 12 to 21MPa.A relationship between τ° and ΔE*i/E*R is proposed.Critical examination of these data infers that kaolin powder dispersed in solid rubber matrix acts as an additive which decreases the random movement of the polybutadiene chains.Consequently,dispersions of nano-particles in liquid and in solid SBR are considered to be related,thus leading to a rheological method for selecting nano-particles as fillers in solid SBR. 相似文献
Commercially available 1,2‐PB was transformed into a well‐defined reactive intermediate by quantitative bromination. The brominated polymer was used as a polyfunctional macroinitiator for the cationic ring‐opening polymerization of 2‐ethyl‐2‐oxazoline to yield a water‐soluble brush polymer. Nucleophilic substitution of bromide by 1‐methyl imidazole resulted in the formation of polyelectrolyte copolymers consisting of mixed units of imidazolium, bromo, and double bond. These copolymers, which were soluble in water without forming aggregates, were used as stabilizers in the heterophase polymerization of styrene and were also studied for their ionic conducting properties.