Calculation of Hildebrand solubility parameters of some polymers using QSPR methods based on LS-SVM technique and theoretical molecular descriptors

Nanocomposite Organogel for Art Conservation─A Novel Wax Resin Removal System

We describe a new, safe, and effective method for removing wax resin adhesive from the canvases of paintings conserved by the once widely used Dutch Method, which involved attaching a new canvas to the back of a painting using an adhesive made of beeswax and natural resin. First, a low-toxicity cleaning mixture for dissolving the adhesive and removing it from the canvases was developed, and then a nanocomposited organogel was obtained. The ability of the organogel to remove the adhesive from canvases was investigated on the lining of the 1878 painting "Battle of Grunwald" by Jan Matejko, with promising results. Additionally, we found that the organogel can be used several times with no visible loss of cleaning ability. Finally, the effectiveness and safety of the method were confirmed on two oil paintings (one from the National Museum in Warsaw): all the wax resin adhesive was removed and the painting regained its original brightness and vivid colors.

Triblock Superabsorbent Polymer Nanocomposites with Enhanced Water Retention Capacities and Rheological Characteristics

Superabsorbent polymers (SAPs) are useful polymers in a wide range of application fields ranging from the hygiene industry to construction and agriculture. As versatility and high water absorption capacity are their important merits, SAPs usually suffer from low water retention capacity (fast release) and weak mechanical properties. To address these drawbacks, a set of new superabsorbent polymer-Halloysite nanotube (HNT) nanocomposites was synthesized via free radical polymerization of acrylamide, 2-acrylamido-2-methylpropane-1-sulfonic acid, and acrylic acid in the presence of vinyltrimethoxysilane (VTMS) as the crosslinker. FTIR and TGA characterizations confirm the polymerization of SAP and successful incorporation of HNTs into the SAP polymer matrix. The effect of the HNT nanofiller amount in the nanocomposite polymer matrix was investigated with swelling-release performance tests, crosslink density calculations, and rheology measurements. It was found that equilibrium swelling ratios are correlated and therefore can be tuned via the crosslink densities of nanocomposites, while water retention capacities are governed by storage moduli. A maximum swelling of 537 g/g was observed when 5 wt % HNT was incorporated, in which the crosslink density is the lowest. Among the SAP nanocomposites prepared, the highest storage modulus was observed when 1 wt % of nanofiller was incorporated, which coincides with the nanocomposite with the longest water retention. The water release duration of SAPs was prolonged up to 27 days with 1% HNT addition in parallel with the achieved maximum storage modulus. Finally, three different incorporation mechanisms of the HNT nanofiller into the SAP nanocomposite structure were proposed and confirmed with rheology measurements. This study provides a rapid synthesis method for SAP nanocomposites with enhanced water retention capacities and explains the relationship between swelling and crosslink density and water retention and mechanical properties of SAP nanocomposites.

Molecular Design of Soluble Biopolyimide with High Rigidity

New soluble biopolyimides were prepared from a diamine derived from an exotic amino acid (4-aminocinnamic acid) with several kinds of tetracarboxylic dianhydride. The biopolyimide molecular structural flexibility was tailored by modifying the tetracarboxylic dianhydride moiety. The obtained polyimides were soluble in various solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, and even tetrahydrofuran. It was observed that the biopolyimide solubility was greatly dependent upon the structural flexibility (torsion energy). Flexible structure facilitated greater solubility. The synthesized biopolyimides were largely amorphous and had number-average molecular weight (M_n) in the range (5–8) × 10⁵. The glass transition temperatures (T_g) of the polymers ranged from 259–294 °C. These polymers exhibited good thermal stability without significant weight loss up to 410 °C. The temperatures at 10% weight loss (T_d10) for synthesized biopolyimide ranged from 375–397 °C.