A strategy is reported for controlling the architecture of poly­(disulfide)­s by ring-opening polymerization. Aryl thiol initiators shift the ring–chain equilibrium to yield cyclic polymers, while alkyl thiols favor linear ones. Control over polymerization enables synthesis of large polymers (630 kDa) and catalytic depolymerization to recycle monomers. This work provides a new avenue to create dynamic covalent polymers with controlled geometry and length, allowing better characterization of structure–property relationships to expand their materials potentials.

Dynamic effects are an important determinant of chemical reactivity and selectivity, but the deliberate manipulation of atomic motions during a chemical transformation is not straightforward. Here, we demonstrate that extrinsic force exerted upon cyclobutanes by stretching pendant polymer chains influences product selectivity through force-imparted nonstatistical dynamic effects on the stepwise ring-opening reaction. The high product stereoselectivity is quantified by carbon-13 labeling and shown to depend on external force, reactant stereochemistry, and intermediate stability. Computational modeling and simulations show that, besides altering energy barriers, the mechanical force activates reactive intramolecular motions nonstatistically, setting up “flyby trajectories” that advance directly to product without isomerization excursions. A mechanistic model incorporating nonstatistical dynamic effects accounts for isomer-dependent mechanochemical stereoselectivity.

Abstract. In order to reduce the secondary damage of melon gum fracturing fluid for the low permeability alkali sensitivity reservoir, Optimized a kind of low molecular weight polymer fracturing fluid, and solve the technical problem of crosslinking time is not easy to control, fracturing fluid gel breaking difficult in low temperature. Through the study of the optimization of main additives, The fracturing fluid use low molecular highly active three yuan low molecular polymer as a thickener, which use of special synthetic process of polymerization with multiple active node. Its molecular weight is 200000 ~ 300000, water soluble speed is fast, site preparation easy, and thickening ability is strong. When the concentration is 0.2% ~ 0.6% in the fracturing fluid ,it can satisfy the requirement of fracturing operation. With organic zirconium and aldehyde compounds as crosslinking agent, The fracturing fluid have been achieved in good results in erlian uli of north China oilfield, ordos basin yishan slope of oil well and gas well fracturing.

Based on the proppant index, a production forecast method for thick oil-bearing formation fracturing was deduced. And combined with NPV methodology, treatment scale of multistage pump-off propped fracturing can be optimized. The effects of treatment parameters, such as injection stages, pumping interval, pumping rate, the ratio of pre and post stage pumping rate, on the fracture geometry, conductivity and production were simulated and analyzed. It reveals that two injection stages, 5 minutes of pumping interval and consistent pumping rate contribute to the highest annual cumulative production. Moreover, the injection stages make the most significant influence on production. Optimization results, applied to Kunbei Oilfield, achieved satisfactory application effects. The single well average production was enhanced by7.92 t/d, the stimulation ratio was 13.56, and the stimulation validity was about 270 days.