Preparation, Structure and Performance of Poly(lactic acid)/Poly(lactic acid)-γ-Cyclodextrin Inclusion Complex-Poly(glycidyl methacrylate) Composites

Characterization of degradation behaviors of PLA biodegradable plastics by infrared spectroscopy

In this paper, the degradation behavior of two kinds of polylactic acid (PLA) biodegradable material products (pure PLA cup cover and modified PLA straw) was studied. It was found that under the composting environment specified in the International Standard, in the first 35 days, the degradation rate of the straw (with 50%-60% poly butylenes succinate (PBS)) was faster than that of the pure PLA cup cover, but in the later stage, the PLA cup cover exceeded the straw and disintegrated preferentially, and both could be degraded in about 70 days. After further analyzing the far-infrared (FIR, can also be called THz) and mid infrared (MIR) spectra of cup cover and straw, we observed that the material structure had not changed until disintegration, only the ester bond was hydrolyzed, the polymers became oligomers, which could be reflected in the change of the effective area of the characteristic peak at 7.15 THz (cup cover, labeled 1921) and 6.99 THz (straw, labeled 4386) in the THz spectrum. With the degradation, the effective area decreased continuously. Due to the strong absorption of the material in MIR band, most characteristic peaks were flattened and lost analytical value. The bivariate correlation of degradation time, biodegradation rate, total carbon dioxide release and the effective area of the characteristic peak at 7.15 THz (1921) and 6.99 THz (4386) in THz spectrum was analyzed by SPSS software. We discovered that the degradation time was significantly positively correlated with biodegradation rate and carbon dioxide release at the level of 0.01 and negatively correlated with the effective area of characteristic peak at the level of 0.05. The biodegradation rate was significantly negatively correlated with the effective area of characteristic peak at the level of 0.01. Taking the degradation time as the independent variable and the biodegradation rate, carbon dioxide release and effective area of characteristic peak as the dependent variables, we got that the THz spectrum could be used to describe the degradation behavior of PLA products as long as appropriate coefficient correction was made. In this way, we could separate from the laboratory environment, study the impact of environmental diversification on material degradation performance, and reduce the cost of material degradation performance identification. Using density functional theory (DFT), reduced density gradient (RDG) method and visualization software, the changes of weak interaction position and intensity in the molecule during the polymerization of lactic acid into PLA were further analyzed. We found that the vibration of ester bond corresponded to the characteristic peak with weak intensity in the spectrum, and the peak with large intensity mainly originated from the out-of-plane swing of O-H bond in the molecule.

Cyclodextrin derivatives used for the separation of boron and the removal of organic pollutants

Adsorption plays an important role in seawater desalination, wastewater treatment, and, especially, boron removal from natural aqueous systems. In this paper, two sponge-like multifunctional polymers based on a cyclodextrin backbone were synthesized and used as adsorbents for the removal of boron, methylene blue (MB), methyl orange (MO), and phenol. The syntheses were carried out by esterification, atom transfer polymerization, and nucleophilic addition reaction. The polymers were characterized by ¹H NMR spectroscopy, IR spectroscopy, XRD, XPS, and SEM. The performance of the two different adsorbents was investigated considering the effect of pH, initial concentration, and the anions and cations in an aqueous solution of borates. The experimental data were fitted with an adsorption isothermal model, adsorption kinetic model and other models. Both adsorbents exhibited high adsorption capacities (B: 31.05 mg/g and 20.45 mg/g, MB: 29.43 mg/g and 32.29 mg/g, MO: 47.36 mg/g and 49.23 mg/g, phenol: 5.04 mg/g and 4.35 mg/g, respectively) and a fast adsorption rate. The boron adsorption was found to be an exothermic process. The adsorbents show promising potential for the removal of boron and benzene-containing organic pollutants from aqueous solution.

Supramolecular Interactions in Hybrid Polylactide Blends-The Structures, Mechanisms and Properties

The conformation of polylactide (PLA) chains can be adjusted by supramolecular interactions (the formation of hydrogen bonds or host-guest complexes) with appropriate organic molecules. The structures formed due to those intermolecular interactions may act as crystal nuclei in the PLA matrix ("soft templating"). In this review, the properties of several supramolecular nucleating systems based on synthetic organic nucleators (arylamides, hydrazides, and 1,3:2,4-dibenzylidene-d-sorbitol) are compared to those achieved with biobased nucleating agents (orotic acid, humic acids, fulvic acids, nanocellulose, and cyclodextrins) that can also improve the mechanical properties of PLA. The PLA nanocomposites containing both types of nucleating agents/additives are discussed and evaluated in the context of their biomedical applicability.