Degradation Of Biodegradable Polymers Research Articles

Biodegradable polymers boost reproduction in the earthworm Eisenia fetida

Microplastic contamination in soil has become a global environmental threat as it adversely affects terrestrial organisms like earthworms as well as soil properties. Especially biodegradable polymers have recently been used as an alternative to conventional polymer types, although their impact remains poorly understood. Thus, we studied the effect of conventional (polystyrene: PS, polyethylene terephthalate: PET, polypropylene: PP) versus aliphatic polyesters classified as biodegradable polymers (poly-(l-lactide): PLLA, polycaprolactone: PCL) on the earthworm Eisenia fetida and soil properties (pH and cation exchange capacity). We addressed direct effects on the weight gain and reproductive success of E. fetida, and indirect effects, like changes in the gut microbial composition as well as the production of short-chain fatty acids by the gut microbiota. Earthworms were exposed for eight weeks in an artificial soil amended with two environmentally relevant concentrations (1 % and 2.5 % (w/w)) of the different microplastic types. PLLA and PCL boosted the number of cocoons produced by 135 % and 54 %, respectively. Additionally, exposure to these two polymers increased number of hatched juveniles, changed gut microbial beta-diversity, and increased the production of the short chain fatty acid lactate compared to the control treatments. Interestingly, we also found a positive effect of PP on the earthworm's bodyweight and reproductive success. The interaction of microplastic and earthworms decreased soil pH by about 1.5 units in the presence of PLLA and PCL. No polymer effect on the cation exchange capacity of soil was found. In general, neither the presence of conventional nor biodegradable polymers had any adverse effects on any of the studied endpoints. Our results suggest that the effects of microplastic highly depend on the polymer type, and that the degradation of biodegradable polymers might be enhanced in the gut of earthworms, which implies that they may use biodegradable polymers as a potential carbon source.

Preparation of Novel Biodegradable Polymer Slow-Release Fertilizers to Improve Nutrient Release Performance and Soil Phosphorus Availability.

Inspired by the gradual collapse of carbon chain and the gradual release of organic elements into the external environment during the degradation of biodegradable polymers, a novel biodegradable polymer slow-release fertilizer containing nutrient nitrogen and phosphorus (PSNP) was prepared in this study. PSNP contains phosphate fragment and urea formaldehyde (UF) fragment, which are prepared by solution condensation reaction. Under the optimal process, the nitrogen (N) and P2O5 contents of PSNP were 22% and 20%, respectively. The expected molecular structure of PSNP was confirmed by SEM, FTIR, XRD, and TG. PSNP can release N and phosphorus (P) nutrients slowly under the action of microorganisms, and the cumulative release rates of N and P in 1 month were only 34.23% and 36.91%, respectively. More importantly, through soil incubation experiment and leaching experiment, it was found that UF fragments released in the degradation process of PSNP can strongly complex soil high-valence metal ions, thus inhibiting the phosphorus nutrient released by degradation to be fixed in the soil and ultimately effectively increasing the soil available P content. Compared with ammonium dihydrogen phosphate (ADP), a small molecule phosphate fertilizer that is easily soluble, the available P content of PSNP in the 20-30 cm soil layer is almost twice that of ADP. Our study provides a simple copolymerization method to prepare PSNP with excellent slow-release N and P nutrients, which can promote the development of sustainable agriculture.

The effects of tensile stress on degradation of biodegradable PLGA membranes: A quantitative study

The inhomogeneous stress distribution of biodegradable stents after implantation affects the local degradation rate of the stents, leading to stress concentration and hence stent fracture. The quantitative relationship between the tensile stress and degradation rate of stent polymer is first investigated in this work. To implement the study, an in vitro degradation of poly(l-lactide-co-glycolide) (PLGA) membranes was incubated in deionized water under different applied tensile stress levels from 0.1 MPa to 0.5 MPa. By a special designed device, the tensile stress level can be maintained constant during degradation. The mass loss and mechanical properties of the membranes during the degradation were sampled each week until the membranes broke. The experimental results showed that over a range of tensile stress, higher tensile stress might lead to quicker loss of mechanical properties. Specifically, remarkable decreases of elastic modulus and tensile strength in 0.5 MPa group were observed. As the magnitude of tensile stress increased, more mass loss was observed in the loaded groups. In conclusion, the mass loss rate and mechanical properties of PLGA was sensitive to the tensile stress level during the in vitro degradation. The load dependency of our data demonstrates the importance of quantifying the effects of tensile stress on the degradation of biodegradable polymers. Moreover, this quantification model could be used as a prediction tool for the optimization of biodegradable polymer stents.

Enzyme-Catalyzed Degradation of Biodegradable Polymers Derived from Trimethylene Carbonate and Glycolide by Lipases from Candida Antarctica and Hog Pancreas

Enzyme-catalyzed degradation of poly(trimethylene carbonate) homo-polymer (PTMC) and poly(trimethylene carbonate-co-glycolide) co-polymer (PTGA) was investigated in the presence of lipases from Candida antarctica and Hog pancreas. Degradation was monitored by gravimetry, size-exclusion chromatography (SEC), nuclear magnetic resonance (NMR), tensiometry and environmental scanning electron microscopy (ESEM). PTMC can be rapidly degraded by Candida antarctica lipase with 98% mass loss after 9 days, while degradation by Hog pancreas lipase leads to 27% mass loss. Introduction of 16% glycolide units in PTMC chains strongly affects the enzymatic degradation. Hog pancreas lipase becomes more effective to PTGA co-polymer with a mass loss of 58% after 9 days, while Candida antarctica lipase seems not able to degrade PTGA. Bimodal molecular weight distributions are observed during enzymatic degradation of both PTMC and PTGA, which can be assigned to the fact that the surface is largely degraded while the internal part remains intact. The composition of the PTGA co-polymer remains constant, and ESEM shows that the polymers are homogeneously eroded during enzymatic degradation. Contact angle measurements confirm the enzymatic degradation mechanism, i.e., enzyme adsorption on the polymer surface followed by enzyme-catalyzed chain cleavage.

On the response of viscoelastic biodegradable polymeric solids

We study the time-dependent response of a biodegradable polymeric solid which has relevance to applications in biomedicine, for example biodegradable polymeric stents. The degradation mechanism of these polymers is primarily due to hydrolysis and high strains/stresses can accelerate the degradation. In order to mimic the environment and the external stimuli which the stent is subject to, the polymers are subject to three different types of external stimuli, that are due to prescribed mechanical loading, the diffusion of water, and the degradation that occurs over a period of time, ensuring that we have a strong coupling between the deformation, degradation, and diffusion response. We assume that the polymer is described by a linearized viscoelastic constitutive model, with material parameters varying due to the degradation, in the case of biodegradable polymers. We study the effect of time-dependent response on the degradation of biodegradable polymers. We also analyze an initial-boundary value problem corresponding to a cylindrical annulus of a biodegradable viscoelastic polymeric solid of finite length, the geometry that is relevant to a biodegradable stent, in contact with another cylindrical annulus (the arterial wall) of viscoelastic solid. The stent is subject to internal radial pressure, and the diffusion of a fluid, while the arterial wall is subjected to external radial pressure. We examine the coupling between the response of the biodegradable stent and the arterial wall. This is done in order to support the design of biodegradable polymeric stents by considering reasonably realistic geometrical and material models.

Thermal analysis of hydrolysis and degradation of biodegradable polymer and bio-composites

The purpose of this study was to conduct a thermal analysis of the hydrolysis and degradation behavior of biodegradable polymers and bio-composites at 50°C and 90% relative humidity (RH). With increasing hydrolysis time, the thermal stability and degradation temperature of polybutylene succinate (PBS) slightly decreased. The glass transition temperature (Tg) and melting temperature (Tm) of PBS and the anti-hydrolysis agent treated PBS did not vary significantly with increasing hydrolysis time, whereas those of the trimethylolpropane triacrylate (TMPTA)-treated PBS slightly increased. With increasing hydrolysis time, the storage modulus (E’) values of the bio-composites decreased, whereas those of the TMPTA treated bio-composites slightly increased. Also, the tan values of the anti-hydrolysis agent and TMPTA treated PBS-BF bio-composites were slightly lower than those of the non-treated bio-composites, due to the reduction in their degree of hydrolysis. The tanδmax peak temperature (Tg) of the anti-hydrolysis agent treated bio-composites was not significantly changed, whereas that of the TMPTA treated bio-composites was increased.

Surface Morphology and Enzymatic Degradation of Biodegradable Polymers

Surface Morphology and Enzymatic Degradation of Biodegradable Polymers

Calculation of hydrolytic rate constants of poly(ortho ester)s from molecular weights determined by gel permeation chromatography.

To obtained rate constants from weight-averaged (Mw) or z-averaged (Mz) molecular weights for polymers of Schule-Flory distribution and undergoing random scission. These constants were compared with those obtained by parallel 1HNMR studies. The hydrolysis of two poly(ortho ester)s were followed by 1HNMR and gel permeation chromatography (GPC). Equations to convert number-averaged (Mn), Mw and Mz into fraction of backbone remaining (fc) were derived. First-order hydrolytic rate constants of two poly(ortho ester)s; DETOSU-HD and DETOSU-CDM were calculated using these relationships. The rate constants calculated from 1HNMR, Mz and Mw were 0.215, 0.21 and 0.182 hr-1, respectively, for DETOSU-CDM and 0.152, 0.086 and 0.038 hr-1 for DETOSU-HD. The large discrepancy in the rates determined by 1HNMR and GPC in the latter case was attributed to that the detector response (refractive index) of the monomers was lower than that of the high molecular weight polymer. The difference is small in the case of DETOSU-CDM, and the rates calculated from GPC data were comparable or nearly identical to that obtained from 1HNMR data. Although GPC can yield rapid and valuable kinetic data for the degradation of biodegradable polymers, the system, however, must be carefully calibrated to account for the variations in Mark-Houwink coefficients and in the response of the mass detector between the high and low MW polymers.