Evolution of supramolecular healable composites: a minireview

Efforts to further extend the range of applications of polymer based materials have resulted in the recent production of healable polymers that can regain their strength after damage. Within this field of healable materials, supramolecular polymers have been subject to extensive investigation. By virtue of their reversible non-covalent interactions, cracks and fractures in such polymers can be readily and repeatedly healed in order to regain key physical properties. However, many supramolecular polymers are relatively weak and elastomeric in nature, which renders them unsuitable for high strength structural applications. To overcome these deficiencies, preliminary studies have shown that it is possible to reinforce supramolecular polymers with microscale and nanoscale fillers to afford composites that are not only stronger and stiffer compared with the polymers alone but also retain their healing abilities. In this minireview we discuss the evolution of these supramolecular composites and their advantages over more conventional, covalent polymeric materials

Molecular recognition between functionalized gold nanoparticles and healable, supramolecular polymer blends – a route to property enhancement

A new, healable, supramolecular nanocomposite material has been developed and evaluated. The material comprises a blend of three components: a pyrene-functionalized polyamide, a polydiimide and pyrene- functionalized gold nanoparticles (P-AuNPs). The polymeric components interact by forming well-defined p–p stacked complexes between p-electron rich pyrenyl residues and p-electron deficient polydiimide residues. Solution studies in the mixed solvent chloroform–hexafluoroisopropanol (6 : 1, v/v) show that mixing the three components (each of which is soluble in isolation), results in the precipitation of a supramolecular, polymer nanocomposite network. The precipitate thus formed can be re-dissolved on heating, with the thermoreversible dissolution/precipitation procedure repeatable over at least 5 cycles. Robust, self-supporting composite films containing up to 15 wt% P-AuNPs could be cast from 2,2,2- trichloroethanol. Addition of as little as 1.25 wt% P-AuNPs resulted in significantly enhanced mechanical properties compared to the supramolecular blend without nanoparticles. The nanocomposites showed a linear increase in both tensile moduli and ultimate tensile strength with increasing P-AuNP content. All compositions up to 10 wt% P-AuNPs exhibited essentially quantitative healing efficiencies. Control experiments on an analogous nanocomposite material containing dodecylamine-functionalized AuNPs (5 wt%) exhibited a tensile modulus approximately half that of the corresponding nanocomposite that incorporated 5 wt% pyrene functionalized-AuNPs, clearly demonstrating the importance of the designed interactions between the gold filler and the supramolecular polymer matrix

Thermoresponsive supramolecular polymer network comprising pyrene-functionalized gold nanoparticles and a chain-folding polydiimide

A thermoresponsive, supramolecular nanocom- posite has been prepared by the addition of pyrenyl functionalized gold nanoparticles (AuNPs) to a polydiimide that contains receptor residues designed to form defined complexes with pyrene. The novel pyrenyl-functionalized AuNPs (P-AuNPs) were characterized by transmission electron microscopy, with surface functionalization confirmed by infrared and UV-visible spectroscopic analyses. Mixing solutions of the P-AuNPs and a p-electron-deficient poly- diimide resulted in the formation of electronically comple- mentary, chain-folded and p-p-stacked complexes, so affording a new supramolecular nanocomposite network which precipitated from solution. The P-AuNPs bind to the polydiimide via p-p stacking interactions to create supramolecular cross- links. UV-visible spectroscopic analysis confirmed the thermally reversible nature of the complexation process, and transmission electron microscopy (TEM), infrared spectroscopy (IR), and differential scanning calorimetry (DSC) were used to characterize the supramolecular-nanocomposite material. The supramolecular polymer network is insoluble at room temperature, yet may be dissolved at temperatures above 60 °C. The thermal reversibility of this system is maintained over five heat/cool cycles without diminishment of the network characteristics. In contrast to the individual components, the nanocomposite formed self- supporting films, demonstrating the benefit of the supramolecular network in terms of mechanical properties. Control experiments probing the interactions between a model diimide compound that can also form a p-stacked complex with the p- electron rich pyrene units on P-AuNPs showed that, while complexation was readily apparent, precipitation did not occur because a supramolecular cross-linked network system could not be formed with this system

Thermoresponsive Supramolecular Polymer Network Comprising Pyrene-Functionalized Gold Nanoparticles and a Chain-Folding Polydiimide

A thermoresponsive, supramolecular nanocomposite has been prepared by the addition of pyrenyl functionalized gold nanoparticles (AuNPs) to a polydiimide that contains receptor residues designed to form defined complexes with pyrene. The novel pyrenyl-functionalized AuNPs (P-AuNPs) were characterized by transmission electron microscopy, with surface functionalization confirmed by infrared and UV–visible spectroscopic analyses. Mixing solutions of the P-AuNPs and a π-electron-deficient polydiimide resulted in the formation of electronically complementary, chain-folded and π–π-stacked complexes, so affording a new supramolecular nanocomposite network which precipitated from solution. The P-AuNPs bind to the polydiimide via π–π stacking interactions to create supramolecular cross-links. UV–visible spectroscopic analysis confirmed the thermally reversible nature of the complexation process, and transmission electron microscopy (TEM), infrared spectroscopy (IR), and differential scanning calorimetry (DSC) were used to characterize the supramolecular-nanocomposite material. The supramolecular polymer network is insoluble at room temperature, yet may be dissolved at temperatures above 60 °C. The thermal reversibility of this system is maintained over five heat/cool cycles without diminishment of the network characteristics. In contrast to the individual components, the nanocomposite formed self-supporting films, demonstrating the benefit of the supramolecular network in terms of mechanical properties. Control experiments probing the interactions between a model diimide compound that can also form a π-stacked complex with the π-electron rich pyrene units on P-AuNPs showed that, while complexation was readily apparent, precipitation did not occur because a supramolecular cross-linked network system could not be formed with this system

Year-wise snakebites and death summary.

<p>From the study population, the information about the year of snakebite was obtained from the household members. The information obtained is presented accordingly for each type of study village.</p

Circumstances of snakebites and their socio-economic impacts.

<p>The circumstances of snakebite such as where and when the bite occurred, the activities of victims during bite and the place of bite on the body were obtained from the victims. In addition, the direct costs involved in the treatment of snakebites and their socio-economic impacts were also assessed. The information provided here was from 129 interviewed victims and percentages were calculated accordingly.</p

Distribution of snake bites by age group.

<p>The red bars show the % of the total number of people which are in each age group identified in the study population. The blue bars show the % of the population of that age group who have been bitten by snakes.</p

Distribution of snake bites by type of snake.

<p>Where the snake species was not identified due to the inability of people to identify the snake, or the bite occurred in dark, these are classified as ‘unknown’.</p

Analysis of tibialis anterior muscle regeneration after administration of CAMP or CTX.

A, H and E staining of muscle identifying centrally located fibre nuclei (CLN) (arrows) and (B) quantification of centrally located muscle fibre size 5 days post administration. C, H and E staining of muscle (arrows) and (D) quantification of centrally located muscle fibre size 10 days post administration. E, intra-fibre IgG localisation for necrotic muscle fibres (arrows) and quantification of necrotic fibre density (F) and size (G) 5 days post administration. H, intra-fibre IgG localisation for necrotic fibres (arrows) and (I) quantification of necrotic fibre density 10 days post administration. J, identification of regenerating muscle fibres through the expression of MYH3 (arrows) and quantification of regenerating muscle fibre density (K) and size (L) 5 days post administration. M, identification of regenerating muscle fibres through the expression of MYH3 (arrows) and quantification of regenerating muscle fibre density (N) and size (O) 10 days post administration. P, Localisation of endothelial marker CD31 and (Q) quantification of capillaries per regenerating muscle fibre 5 days post administration. R, localisation of endothelial marker CD31 and (S) quantification of capillaries per regenerating muscle fibre 10 days post administration. T, immunostaining with antibody F4/80 and (U) its density quantification in damaged region 5 days post administration. V, immunostaining with antibody F4/80 and (W) its density quantification in damaged region 10 days post administration. Data represent mean ± S.D. (n = 5 for each cohort). The p values shown are as calculated by two-tailed Student’s T test for independent variables using GraphPad Prism (*p<0.05, **p<0.01 and ***p<0.001).</p

Macrostructure of tibialis anterior muscle after CAMP treatment.

A, representative images of muscles treated with either CTX or CAMP for 5 or 10 days. Quantification of TA weight at 5 (B) and 10 (C) days post administration. Scale bar represents 5 mm. Data represent mean ± S.D. (n = 5 for each cohort). The p values shown are as calculated by One-way ANOVA followed by post hoc Tukey's test using GraphPad Prism (*p<0.05, **p<0.01 and ***p<0.001).</p