The dissociation of an amino acid, referring to the readiness with which it releases a proton (H+), varies based on the amino acid's side chain. Among the amino acids, those with acidic side chains, like glutamate and aspartate, dissociate more readily compared to others due to their lower pKa values. The pKa value of an amino acid side chain is a measure of its acidity; the lower the pKa, the stronger the acid, and thus, the more readily it will donate a proton to the surrounding environment. Aspartate and glutamate, which have side chains with carboxylic acid groups, have pKa values in the range of about 3.65 and 4.25 respectively, making them more likely to donate protons under physiological pH (around 7.4). This is in contrast to amino acids with neutral or basic side chains, whose pKa values make them less likely to dissociate under the same conditions. Therefore, in terms of dissociation in a biological context, acidic amino acids like glutamate and aspartate are more likely to release a proton, influencing various biochemical processes, including protein folding, enzyme activity, and cell signaling.

Polyethylene Glycol (PEG) is a synthetic, petroleum-based compound derived through a process known as polymerization of ethylene oxide. It is not sourced from natural ingredients but is manufactured in a laboratory or industrial setting. PEGs are known for their versatility and are used in numerous products, including medical applications, cosmetics, and pharmaceuticals, due to their ability to enhance moisture retention and promote solubility. Despite being synthetic, PEGs are widely researched and considered safe for use in various applications, although individuals with sensitive skin may sometimes experience irritation. The synthetic nature of PEG raises discussions about sustainability and environmental impact, leading some to seek natural alternatives in formulations.

The solubility of polymers depends on several factors including their chemical structure, molecular weight, and the solvent in question. Generally, like dissolves like; hence, polar polymers are more likely to dissolve in polar solvents, and non-polar polymers in non-polar solvents. However, polymer chains can have various side groups affecting their overall polarity and solubility. High molecular weight polymers are less soluble due to increased intermolecular forces. Moreover, cross-linked polymers, such as vulcanized rubber, are insoluble in most solvents due to their three-dimensional network structures. It's also essential to consider temperature; some polymers may only dissolve at elevated temperatures. In practice, the solubility of a specific polymer must be evaluated in the context of its chemical structure and the solvent used.