A new highly reactive isobutyl lactide monomer (IBL) was synthesized with the ring closing of halogenated carboxylic acid acquired by the reaction of (S)-2-hydroxy-4-methylpentanoic acid with 2-bromopropionyl bromide. A desired thermosensitive and injectable PEG-based poly(isobutyl lactide) di-and triblock copolymers (MePEG-PIBL and PIBL-PEG-PIBL), a promising alternative to customary PEG-based PLA and PLGA block copolymers, have been synthesized with narrow polydispersities as low as 1.08, high conversions up to 99%, and suitable hydrophilic/ hydrophobic balances for gel−sol applications by ring-opening polymerization at 120 °C. The polymerization rate of MePEG-PIBL was found to be the highest among other PEG-based substituted glycolides (MePEG-PDIBG, MePEG-PIPL, and MePEG-PDIPG) due to having a single and less hindered secondary β-carbon atom (R 2 CH 2 ) in IBL. The mechanism of poly(asymmetrical glycolide)s was also illuminated by single-frequency decoupled 1 H NMR, 13 C NMR, and optical rotation analyses by taking into account the effect of substituents on symmetrical and asymmetrical glycolides. PIBL units of the block copolymers showed an amorphous phase, critical for desired drug release rate, in thermal analyses. Thus, PIBL-based copolymer gels displayed a more effective release profile of paclitaxel (up to 57%) than semi-crystalline PLLA-PEG gels (up to 5.7%) in 2 weeks. The location of PEG, present as an internal or lateral component in copolymers, also affected the rate of hydrolitic degradation (34.6% vs 23.7% degradation of PIBL units in di-and triblock copolymers, respectively). According to the results of cell viability assays (WST-1 test and live/dead assay), where L929 and human primary dermal fibroblasts were tested, the triblock copolymer did not cause any cell damages or cell morphological changes in all concentration ranges tested (0.1−3.0 mg mL −1 ). The aqueous solutions of these copolymers exhibited very well temperature-dependent reversible gel−sol transitions for use in a localized drug delivery system.

Purpose This study aims to perform the surface treatment of synthetic α-Fe2O3 red iron oxide pigment with hydrolysate 3-aminopropyl silane (A) and colloidal silica (CS) and investigate the effects of surface-treated pigment on the styrene acrylic (SA) emulsion and polyurethane (PU) dispersion. Design/methodology/approach For this purpose, firstly red iron oxide particles were modified with A and CS separately in an aqueous medium. After isolation of the modified iron oxide were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). Moreover, the degree of the dispersion stability of the modified pigment in coatings with SA emulsion and PU dispersion was investigated by using an oscillation rheometer. Loss (G''), storage (G') modulus, loss factor [tan(δ)] and yield stress (τ0) values were determined by performing amplitude and frequency sweep tests. Findings The τ0 in SA coatings decreases with the amount of used A and increases with the amount of used CS. The τ0 decreases as the amount of used A and CS in PU coatings increases. The use of CS on red iron oxide pigments causes storage modulus to increase in SA coatings at low angular frequencies, while it causes a decrease in PU coatings. Originality/value To the best of the authors’ knowledge, for the first time, the suspended state of the iron oxide hybrid pigment formed with CS in the coating was investigated rheologically in this study.

In conjunction with the rise in cancer incidence-mortality and handicaps of conventional poly(ethylene glycol)-based polylactide, poly(lactide-co-glycolide), or poly(ɛ-caprolactone) (PEG-based PLA, PLGA, or PCL) injectable thermoresponsive hydrogel platforms, formulating novel biomaterials...