Ring opening polymerization of l-lactide initiated by creatinine

Synthesis of Acrylate Dual-Tone Resists and the Effect of Their Molecular Weight on Lithography Performance and Mechanism: An Investigation

Acrylate photoresists have gained considerable attention in recent years owing to their high resolution, high sensitivity, and versality. In this work, a series of thermally stable copolymers are synthesized by introducing an isobornyl group, and well characterized using Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectra (¹H-NMR). The effects of polymerization conditions on the molecular weight and their further influence on lithography are explored. By analyzing the thermal properties, film-forming capabilities, and the patterning behavior of these copolymers, a direct correlation between lithography performance and polymerization conditions is established via the molecular weight. In addition, the baking temperature of lithography is also optimized by atomic force microscopy (AFM), after which a line resolution of 0.1 μm is observed under the exposure of a 248 nm UV light and electron beam. Notably, our synthesized photoresist displays dual-tone resist characteristics when different developers are applied, and the reaction mechanism of acid-catalyzed hydrolysis is finally proposed by comparing the structural changes before and after exposure.

Synchronous construction of a porous intramolecular D-A conjugated polymer via electron donors for superior photocatalytic decontamination

The development of conjugated polymers with intramolecular donor-acceptor (D-A) units has the capacity to enhance the photocatalytic performance of carbon nitride (g-C₃N₄) for the removal of antibiotics from ambient ecosystems. This strategy addresses the challenge of narrowing the band gap of g-C₃N₄ while maintaining its high LUMO position. For this study, we introduced the above donor units into g-C₃N₄ to construct intramolecular D-A structures through the copolymerization of dicyandiamide with creatinine, which strategically extended light absorption into the green region and expedited photoelectron separation. The introduction of electron donor blocks kept the LUMO distributed on the melem, which maintained the high LUMO energy level of the copolymer with the potential to generate oxygen radicals. The as-prepared porous D-A conjugated polymer enhanced the photocatalytic degradation of sulfisoxazole with kinetic constants 5.6 times higher than that of g-C₃N₄ under blue light and 15.3 times higher under green light. Furthermore, we surveyed the degradation mechanism including the effective active species and degradation pathways. This study offers a new perspective for the synchronous construction of a porous intramolecular D-A conjugated polymer to enhance water treatment and environmental remediation capacities.

Progresses in synthetic technology development for the production of L-lactide

L-Lactide is an intermediate for the industrial production of polylactic acid (PLA). The chemical and optical purities of lactide determine the quality of the prepared PLA. It is of great challenge to synthesize L-lactide efficiently with high chemical and optical purities under the conditions applicable for industrial production. With the national plastic reduction order issued, developing biodegradable materials such as PLA has gradually become a hot topic, and the production of upstream lactide is the key technique for the whole industrial chain. This mini-review aims to summarize typical works on the related synthetic technology development in recent years.

Role of important parameters in ring opening polymerization of polylactide

Different parameters, namely polymerization temperature, polymerization time, monomer/initiator ratio, nature of the initiator, amount of water or other impurities etc. are very significant for polymerization reactions either in bulk or solution. Monomer to initiator ratio has a very significant role in polymerization reactions and a value ranging from 50 to 5000 that has been reported by different researchers. Recrystallization of the monomer removes the meso compounds from the monomer, which absorbs the moisture and effects polymerization reaction. So, it is necessary to recrystallize the monomer with any anhydrous solvent like dry toluene, ethyl acetate etc. Prolonged reaction time cannot increase the polymer yield; it generally causes the decrease of molecular weight and broadening of molecular weight distribution of formed polymers. This is probably due to the transesterification side reaction in polymerization, intensifying at prolonged time periods. Several groups like hydroxyl and carboxylic acid affect the polymerization rate.

Preparation and characterization of polyester- and poly(ester-carbonate)-paclitaxel conjugates

The polyester- and poly(ester-carbonate)-paclitaxel conjugates with low molecular weight were synthesized using dicyclohexylcarbodiimide (DCC) and dimethylaminopyridine (DMAP) as catalysts. Polymeric matrices were obtained by ring-opening polymerization of ɛ-caprolactone (CL), rac-lactide (rac-LA), l-lactide (LLA) and trimethylene carbonate (TMC). The macromolecular conjugates were characterized by using spectroscopic techniques, such as (1)H, (13)C NMR and FTIR. The degree of degradation of polyester- and poly(ester-carbonate)-paclitaxel conjugates was tested in vitro under different conditions. The preliminary results of drug release were discussed.

Seeking polymeric prodrugs of norfloxacin. Part 2. Synthesis and structural analysis of polyurethane conjugates

Oligo(ε-caprolactone) and oligolactide were synthesized via ring-opening polymerization of cyclic esters in the presence of creatinine as initiators. Thus obtained oligomers were successfully used in the synthesis of novel polyurethane conjugates of norfloxacin. The structures of the polymers and conjugates were elucidated by means of MALDI-TOF MS, NMR and IR studies.

Polymerization of cyclic esters initiated by carnitine and tin (II) octoate

Low-molecular weight poly(ε-caprolactone), polylactides and copolymers of ε−caprolactone and lactides were obtained by the polymerization of cyclic esters in the presence of a carnitine/SnOct₂ system. Their structures were proven by means of MALDI−TOF, IR and NMR studies. Effects of temperature, reaction time and carnitine dosage on the polymerization process were examined.

Preparation of porous biodegradable poly(lactide-co-glycolide)/ hyaluronic acid blend scaffolds: characterization, in vitro cells culture and degradation behaviors

A series of poly(lactide-co-glycolide) (PLGA)/ hyaluronic acid (HA) blend with different HA composition were used to fabricate scaffolds successfully. The pores of the three dimensional scaffold were prepared by particle leaching and freeze drying. The pore size was about 50-200 microm and the porosity was about 85%. The characterizations of the scaffold, such as mechanical properties, hydrophilicity and surface morphologies were determined. Mouse 3T3 fibroblast was directly seeded on the scaffolds. The cell adhesion efficiency, cell morphology observed by scanning electron microscopy (SEM) and the degradation behavior of the blend scaffold were evaluated. In summary, the results show that the adhesion efficiency of cells on the PLGA/HA blend scaffold is higher than that on the PLGA scaffold. Moreover, the incorporation of HA in PLGA not only helps to increase the cell affinity but also tends to lead the water and nutrient into the scaffold easily.