Biocompatible and biodegradable block copolymers composed of poly­(ethylene glycol) (PEG) and aliphatic polyester are a class of promising biomaterials. Herein, a teaching experiment was designed to furnish undergraduates with a reliable method to synthesize an amphiphilic poly­(ε-caprolactone)-PEG-poly­(ε-caprolactone) (PCL–PEG–PCL) triblock copolymer via ring-opening polymerization of ε-caprolactone using PEG as the macroinitiator and diphenyl phosphate as the green organocatalyst; the concentrated solution of synthetic polymer in water was then demonstrated as an injectable thermogel with a sol–gel transition upon heating. Ten students serving as volunteers successfully synthesized PCL–PEG–PCL copolymer, and then analyzed their specimens using various techniques including proton-nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry, and X-ray diffraction and learned the principles of instruments. Finally, students prepared an aqueous polymer solution, and observed its interesting spontaneous physical gelation upon heating via the tube-inverting approach and dynamic rheological analysis. The experimental features captured the students’ attention and made them more enthusiastic participants. This newly designed teaching experiment afforded senior undergraduates an excellent opportunity to consolidate basic concepts and principles in books with practical experimental sessions in the field of polymer chemistry, analytical chemistry, and materials science.

Degradability of biomaterials brings many opportunities as well as great challenges to their clinical applications. However, reports of systematic in vivo biodegradation are rather limited due to lack of adequate methodology for real‐time observations. Herein, a tri‐modal bioimaging technique is developed, enabling real time monitoring of biodegradation of synthetic polymers in vivo. The demonstrated material is a successful preclinical poly(lactic acid‐co‐glycolic acid)‐b‐poly(ethylene glycol)‐b‐poly(lactic acid‐co‐glycolic acid) thermosensitive hydrogel that undergoes a spontaneous sol–gel transition upon heating. A macromolecular fluorescence probe and a contrast agent of magnetic resonance imaging (MRI) are designed and synthesized. After subcutaneous injection of the hydrogel containing the two probes into mice, the degradation behaviors of the material are longitudinally and noninvasively tracked via the collaborative application of ultrasound, fluorescence, and MRI. Integrating the noninvasive imaging with the traditional anatomic observations, a three‐stage degradation mechanism of such a hydrogel is proposed for the first time. Also, the dissolved polymers and degradation products in the body are mainly eliminated via liver, gallbladder, and spleen. This work has great value for promoting the future clinical application of these kind of promising hydrogels. Meanwhile, this technological platform provides beneficial inspiration and methodology to investigate in vivo fate of biomaterials.

A series of amphiphilic triblock copolymers composed of poly(ethylene glycol) (PEG) and poly(ε-caprolactone-co-5-alkyl δlactone)s bearing distinct alkyl side groups were synthesized via ringopening copolymerization of ε-caprolactone and a small amount of various 5-alkyl δ-lactones using PEG as the macroinitiator and metalfree diphenyl phosphate as the catalyst. The analysis of 1 H NMR, GPC, DSC, and XRD confirmed that the synthetic copolymers had similar molecular weights and bulk properties; nevertheless, they exhibited quite different aqueous behaviors in response to temperature variations. While the polyesters without side chains simply presented a free-flowing sol over the entire examined temperature range, those bearing methyl or n-propyl side groups underwent a sol−gel transition upon heating and harvested a reversed thermosensitive hydrogel (T-Gel). Meanwhile, the sol−gel transition temperature of the polymer/water system could be easily tailored by adjusting the content of the n-propyl side group. In contrast, the polyesters containing longer n-amyl side groups formed a normal hydrogel (N-Gel) exhibiting a gel−sol (suspension) transition upon heating. Their different aqueous behaviors stemmed from the difference in the hydrophilic−hydrophobic equilibrium of the amphiphilic copolymers. The sol−gel transitions of the thermosensitive hydrogels were attributed to the aggregation of micelles and the dehydration of PEG. The copolymers bearing n-propyl side groups had good cytocompatibility and were fairly stable in a phosphate buffered saline for 80 days, whereas the formed thermosensitive hydrogel (20 wt %) was rapidly degraded via surface erosion within half a month after subcutaneous injection into mice. Consequently, this study indicates that subtle variation in the length of hydrophobic side chains plays a decisive role in the physical gelation of PEG/polyester copolymers. In addition, the thermosensitive hydrogels have the potential for drug and cell delivery based on their good biocompatibility and biodegradability.

The allocation pattern of plant biomass presents the strategy of the plant community to adopt environmental changes, while the driver of biomass allocation is still unclear in degraded alpine grassland ecosystems. To explore the issue, this study investigated the shoot-to-root (R/S) ratio, plant aboveground traits, and root competition of three functional groups (i.e., grasses, sedges, and forbs) at three degradation levels (i.e., no obvious degradation, ND; moderate degradation, MD; and severe degradation, SD) in an alpine meadow in the eastern Qinghai-Tibetan Plateau. The relationships among plant aboveground traits, root competition, and R/S ratio were tested using the structural equation model (SEM). The results showed that the shoot and root biomass tended to decrease, but the R/S ratio of the plant community did not change along the degradation gradient. Plant height, lateral spread, and leaf length of most plant functional groups reduced, while leaf width and leaf area of most plant functional groups did not change along the degradation gradients. The root competition ability (presented as the fraction of root biomass in total biomass) of sedges in MD was the lowest, while that of grasses was the highest. The effects of aboveground competition on the R/S ratio were non-linear because of the different roles of plant height, lateral spread, and leaf area in regulating the R/S ratio along the degradation gradient. In contrast, the effects of belowground competition on the R/S ratio were linear because belowground competition promoted the R/S ratio, and the strength of this effect reduced along the degradation gradient. These results indicate that plant competition might be a critical factor to maintain the high R/S ratio in degraded alpine meadows.

Microbial colonization leads to the formation of biological soil crusts (BSCs) on the surface of architecture, which causes the deterioration of construction materials. However, little information is available on the formation of BSCs on lime concrete materials of early architecture. In this study, the variances of microbial communities, physicochemical properties, and surrounding environmental factors of the lime concrete facades from the early architecture of Wuhan University were investigated. It was found that the surface of lime concrete materials was internally porous and permeable, embedded with biofilms of cyanobacteria, mosses, bacteria, and fungi. Redundancy analysis (RDA) analysis showed that the abundances of photoautotrophic microorganisms depended on light intensity and moisture content of construction materials, while that of heterotrophic microorganisms depended on total nitrogen (TN) and NO3−-N content. The deposition of total carbon (TC), NH4+-N, and total organic carbon (TOC) was mainly generated by photoautotrophic microorganisms. The lime concrete surface of early architecture allowed internal growth of microorganisms and excretion of metabolites, which promoted the biodeterioration of lime concrete materials.