A novel monomer for the synthesis of polyimides, 5-methyl-1,3-phenylene-bis-4-oxyphthalic acid dianhydride was developed. The synthesis was carried out in three stages: the reaction of nucleophilic nitro substitution of 4-nitrophthalonitrile with 5‑methylresorcinol (orcinol) potassium salt and subsequent hydrolysis of the nitrile groups have afforded 5‑methyl-1,3-phenylene-bis-4-oxyphthalic acid, dehydration of which has given the corresponding dianhydride. A series of new thermoplastic high molecular weight polyetherimides based on 5-methyl-1,3-phenylene-bis-4-oxyphthalic acid dianhydride and several aromatic diamines of various structures were synthesized by the method of one-stage catalytic polycondensation in a benzoic acid melt. Inherent viscosity and weight-average molecular mass of the polyetherimides have been of 0.28‒1.20 dL/g and (33‒114) × 10³, respectively. The polyetherimides have been soluble in chloroform, THF, DMF, DMAA, N-methylpyrrolidone, and DMSO and have revealed film-forming properties. According to the DSC and wide-angle X-ray scattering data, the polyetherimides have been found completely amorphous, the glass transition temperature being in the 185–307°C range.

Rising hypersensitivity to PEG and accelerated blood clearance highlight the need for alternative charge‐neutral hydrophilic polymers. Poly(ylide)s represent a class of hydrophilic polymers with biocompatibility and antifouling properties. Here, we explore poly(iminopyridinium ylide) (PIPY) as a versatile nano‐ and biomedical building block. PIPY is synthesized via post‐polymerization modification of poly(pentafluorophenyl acrylate), maintaining a narrow molecular weight distribution. PIPY's structure was confirmed by NMR, FTIR, and SEC. PIPY is soluble in water, saline, MeOH, and DMSO, and remains stable from strongly acidic to physiological pH. Critical aggregation concentration and DOSY NMR measurements indicate an anti‐polyelectrolyte effect and minimal responsiveness to apolar environments, respectively. Notably, PIPY exhibits minimal, entropically driven binding to biomolecules such as bovine serum albumin and lysozyme. This low interaction is critical for its ability to prevent insulin fibrillation upon heating, suggesting utility as a protein‐stabilizing matrix. These combined properties position PIPY as a promising material for future bio‐ and nanomedical applications.