Multiblock Copolymers of Norbornene and Cyclododecene: Chain Structure and Properties.

We investigate the structure-property relations of the multiblock copolymers of norbornene with cyclododecene synthesized via the macromolecular cross-metathesis reaction between amorphous polynorbornene and semicrystalline polydodecenamer in the presence of the first-generation Grubbs catalyst. By adjusting the reaction time, catalyst amount, and composition of the initial system, we obtain a set of statistical multiblock copolymers that differ in the composition and average length of norbornene and dodecenylene unit sequences. Structural, thermal, and mechanical characterization of the copolymers with NMR, XRD, DSC (including thermal fractionation by successive self-nucleation and annealing), and rotational rheology allows us to relate the reaction conditions to the average length of crystallizable unit sequences, thicknesses of corresponding lamellas, and temperatures of their melting. We demonstrate that isolated dodecenylene units can be incorporated into crystalline lamellas so that even nearly random copolymers should retain crystallinity. Weak high-temperature endotherms observed in the multiblock copolymers of norbornene with cyclododecene and other cycloolefins could indicate that the corresponding systems are microphase-separated in the melt state.

Effect of Composition and Interfacial Tension on the Rheology and Morphology of Heavy Oil-In-Water Emulsions.

Rheological and morphological properties of heavy crude oil-in-water (O/W) emulsions have been studied. Two series of emulsions were considered: first, the surfactant type remained constant, while the continuous phase content was varied and second, the surfactant type was varied while the continuous phase content remained constant. Under stress-controlled shearing, all samples exhibit viscoplastic behavior. The rheological properties are directly related to the morphology of the emulsions which vary in size of dispersed phase droplets and their inherent structure. Adding a surfactant characterized by a high value of interfacial oil-water tension results in a decrease in the yield stress (which is a measure of the interparticulate structure strength). The same effect is attained by increasing the water content. Meanwhile, these two factors determine the viscosity which can be much lower than that of the basic heavy crude oil if the O/W type of emulsions has been created. Special attention was paid to the viscoelastic properties which have been scarcely reported. Correlations were found between the surfactant properties, composition of the emulsion, and rheological characteristics of emulsions (yield stress, apparent viscosity, and viscoelastic properties), which allows for reduction in the crude oil viscosity down to a low enough level acceptable for pipe transportation.