Molecular Dynamics in the Crystalline Regions of Poly(ethylene oxide) Containing a Well-Defined Point Defect in the Middle of the Polymer Chain

A Molecular Dynamics Simulation of Polymers’ Interactions with Kaolinite (010) Surfaces in Saline Solutions

The search for polymers that meet the demands of the water recovery process in mining is a contingent challenge. Both the presence of clays and saline waters can impair water recovery from tailings when conventional flocculants are used. In this work, the adsorption of polyacrylamide (PAM), hydrolyzed polyacrylamide (HPAM), poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS), polyacrylic acid (PAA), polyethylene oxide (PEO), and guar gum (GUAR) on a kaolinite surface (010) was investigated using classical molecular dynamics. The results show that the presence of sodium chloride modifies the affinities of the polymers with kaolinite (010). At low salt concentrations, the PAM and GUAR polymers generally show higher adsorption due to the formation of hydrogen bridges. However, the highest adsorptions occur in salt solutions in the presence of HPAM by cationic bridging with sodium ions as a mediator. This high affinity of HPAM is not efficient for flocculation because it re-disperses the particles, but it is promising for the design of new additives produced by grafting HPAM groups onto advanced polymers.

Defects and defect engineering in Soft Matter

Soft matter covers a wide range of materials based on linear or branched polymers, gels and rubbers, amphiphilic (macro)molecules, colloids, and self-assembled structures. These materials have applications in various industries, all highly important for our daily life, and they control all biological functions; therefore, controlling and tailoring their properties is crucial. One way to approach this target is defect engineering, which aims to control defects in the material's structure, and/or to purposely add defects into it to trigger specific functions. While this approach has been a striking success story in crystalline inorganic hard matter, both for mechanical and electronic properties, and has also been applied to organic hard materials, defect engineering is rarely used in soft matter design. In this review, we present a survey on investigations on defects and/or defect engineering in nine classes of soft matter composed of liquid crystals, colloids, linear polymers with moderate degree of branching, hyperbranched polymers and dendrimers, conjugated polymers, polymeric networks, self-assembled amphiphiles and proteins, block copolymers and supramolecular polymers. This overview proposes a promising role of this approach for tuning the properties of soft matter.

Data on tensile tests and NMR measurements of poly(vinilidene fluoride) before and after stress relaxation

Poly(vinilidene fluoride) was characterized before and after stress relaxation by tensile tests and time-domain nuclear magnetic resonance (TD-NMR). Tensile tests were performed to provide mechanical properties, focused on the data of elastic modulus for this matter. The TD-NMR technique was used to calculate the fraction of crystalline, constrained amorphous and free amorphous phase, and the transversal relaxation time of each of these phases.

Chain Tilt and Crystallization of Ethylene Oxide Oligomers with Midchain Defects

Many text books and publications do not focus on the necessity of chain tilting in crystalline lamellae of oligomers and polymers, a fundamental aspect of their crystallization already discussed by Flory. Herein we investigate the chain tilt of ethylene oxide oligomers (EOs) containing various midchain defects by WAXS, SAXS and solid state ¹³C MAS NMR spectroscopy. At low temperatures, one out of the two EO chains of EO₉-meta-EO₉ and EO₁₁-TR-EO₁₁ containing a 1,3-disubstituted benzene or a 1,4-disubstituted 1,2,3-triazole defect in central position of the oligomer chain forms crystals and the other EO chain as well as the defect remain in the amorphous phase. The aromatic midchain defect of these two oligomers can be incorporated into the crystalline lamella upon heating below T_m. Then, the adjoining amorphous EO chain crosses from the lamellae to the amorphous regions at an angle ξ, which is preordained by the substitution pattern of the aromatic defect, revealing that the chain tilt angle ranges between 36° ≤ ϕ ≤ 60°.