Heat Treatment Effect on Biological Behavior of Polyetheretherketone Composites

Polyetheretherketone is a semi-crystalline thermoplastic polymer, that so with heat treatments, it is possible to get different properties which are very important for the material performance. Heat treatment is a broadly utilized to develop the semi-crystalline polymers properties. In the present investigation, annealing of polyetheretherketone (PEEK) was carried out at temperatures above its glass transition temperature (Tg) to study its effects upon the biological conduct of the control and PEEK ternary composites. The bioactivity of the specimens was evaluated by investigating the apatite formation after immersion for different periods in a simulated body fluid (SBF). The biocompatibility of specimens was assessed by MTT assay. Additionally, the antibacterial property of the specimens versus S. aureus was observed with the optical density methods. The results manifested that the formation of hydroxyapatite was obviously observed on specimens after immersion for (7 and 14 days) in the simulated body fluid (SBF). Otherwise, the results of MTT assay recorded the PEEK specimens that excited the activity of fibroblasts, and therefore a high cytocompatibility was noticed and the specimens revealed antibacterial properties against S. aureus. So, the results of the bioactivity, biocompatibility and antibacterial tests in vitro demonstrated that the heat treatment enhanced biological behavior.

Dependence of Crystallization Behavior of Interacting Telechelic Poly(butylene succinate) Oligomer on Molecular Weight

A large spherulite structure deteriorates the mechanical properties of crystalline polymers, and therefore various methods have been explored to increase primary nucleation density. Recently, chain-end modification has been proposed as an effective approach for regulating polymer crystal nucleation. However, the relevant nucleation mechanism still requires investigation. Therefore, in this work, 2-ureido-4[1H]-pyrimidinone (UPy) units, which can form stacks via quadruple hydrogen bonds with each other, are introduced as end groups for the preparation of interacting telechelic poly(butylene succinate) (PBS-UPy) oligomers with different molecular weights (Mns). The crystallization, especially the nucleation behavior of PBS-UPy, is studied in detail by comparing with the corresponding pre-polymer, the hydroxyl-terminal PBS (PBS-OH). The thermal properties of PBS-UPy exhibit similar Mn-dependent tendency to those of PBS-OH, but with weaker total crystallization rate. The spherulite growth rate is significantly reduced, whereas the primary nucleation density is highly promoted, after introducing UPy groups. Further investigation reveals that the mechanism of UPy stacks’ influence on nucleation ability changes from inhibition to promotion with respect to Mn. Even under an inhibition of nucleation ability, the final nucleation density is obviously increased because of a significant decline of the growth rate. In addition, the change in the impact of UPy stacks on nucleation ability is speculated to originate from the memory expression feasibility of ordered conformation in the melt during crystallization.

Engineering Achiral Liquid Crystalline Polymers for Chiral Self-Recovery

Flexible construction of permanently stored supramolecular chirality with stimulus-responsiveness remains a big challenge. Herein, we describe an efficient method to realize the transfer and storage of chirality in intrinsically achiral films of a side-chain polymeric liquid crystal system by combining chiral doping and cross-linking strategy. Even the helical structure was destroyed by UV light irradiation, the memorized chiral information in the covalent network enabled complete self-recovery of the original chiral superstructure. These results allowed the building of a novel chiroptical switch without any additional chiral source in multiple types of liquid crystal polymers, which may be one of the competitive candidates for use in stimulus-responsive chiro-optical devices.