Hydrolysis of PLA-like Plasma Polymer Films with Varying Degree of Crosslinking

Poly-lactide acid (PLA) based biodegradable films are of interest for packaging materials or bioapplications. Plasma-assisted vacuum evaporation technique uses oligomers released during thermal decomposition of source polymer as precursors for plasma polymerization. Conventionally prepared PLA with mw = 10000 g/mol was used as a source polymer. Films were prepared at various RF (13.56 MHz) plasma powers (0-20 W) in order to vary the amount of crosslinking in the film.Swelling and hydrolysis of films were monitored in real time using spectroscopic ellipsometry. The concentration profile of products of hydrolysis was measured by liquid-chromatography (LC-MS). FTIR, XPS and SEM analyses were used for monitoring of film composition and surface characterization. Molecular weights of source polymer and of the plasma polymer were determined by gel-permeation chromatography (GPC). Possibility to prepare PLA-like plasma polymer films with controlled degradability by hydrolysis was demonstrated

Hydrolysis of PLA-like Plasma Polymer Films with Varying Degree of Crosslinking

&lt;p&gt;Poly-lactide acid (PLA) based biodegradable films are of interest for packaging materials or bioapplications. Plasma-assisted vacuum evaporation technique uses oligomers released during thermal decomposition of source polymer as precursors for plasma polymerization. Conventionally prepared PLA with &lt;em&gt;mw&lt;/em&gt; = 10000 g/mol was used as a source polymer. Films were prepared at various RF (13.56 MHz) plasma powers (0-20 W) in order to vary the amount of crosslinking in the film.&lt;/p&gt;&lt;p&gt;Swelling and hydrolysis of films were monitored in real time using spectroscopic ellipsometry. The concentration profile of products of hydrolysis was measured by liquid-chromatography (LC-MS). FTIR, XPS and SEM analyses were used for monitoring of film composition and surface characterization. Molecular weights of source polymer and of the plasma polymer were determined by gel-permeation chromatography (GPC). Possibility to prepare PLA-like plasma polymer films with controlled degradability by hydrolysis was demonstrated.&lt;/p&gt;</jats:p

UV initiated oxidation and chemiluminescence from aromatic-aliphatic co-polyesters and polylactic acid

International audienceThe chemiluminescence of UV irradiated aromatic-aliphatic polyesters (Ecoflex and PBAT) and polylactic acid (PLA) was examined in nitrogen and oxygen atmospheres during the non-isothermal temperature runs in the interval from 40 to 250 °C and isothermally from 150 to 190 °C. The non-isothermal thermogravimetry and FTIR spectroscopy have been used for the characterization of differences in original samples. The temperature maxima of peroxidic peaks in nitrogen scaling their stability were compared and found to be in the order PBAT < Ecoflex < PLA. Their positions on the temperature scale that correlate well with the melting temperature of the respective polymer have been discussed. With prolongation of the UV irradiation period, the intensity of peroxidic peaks increased. On the other hand, the effect of pre-irradiation on non-isothermal runs of chemiluminescence measured in oxygen was not as distinct as for measurements in nitrogen. The deconvolution of the non-isothermal chemiluminescence runs in nitrogen revealed two kinds of peroxides in irradiated samples

Low molecular weight poly(lactic acid) microparticles for controlled release of the herbicide metazachlor: Preparation, morphology, and release kinetics

The preemergence chloroacetamide herbicide metazachlor was encapsulated in biodegradable low molecular weight poly(lactic acid) micro- and submicroparticles, and its release to the water environment was investigated. Three series of particles, S, M, and L, varying in their size (from 0.6 to 8 μm) and with various initial amounts of the active agent (5%, 10%, 20%, 30% w/w) were prepared by the oil-in-water solvent evaporation technique with gelatin as biodegradable surfactant. The encapsulation efficiencies reached were about 60% and appeared to be lower for smaller particles. Generally, it was found that the rate of herbicide release decreased with increasing size of particles. After 30 days the portions of the herbicide released for its highest loading (30% w/w) were 92%, 56%, and 34% for about 0.6, 0.8, and 8 μm particles, respectively. The release rates were also lower for lower herbicide loadings. Metazachlor release from larger particles tended to be a diffusion-controlled process, while for smaller particles the kinetics was strongly influenced by an initial burst release. © 2012 American Chemical Society

Who lived on the Swiss Plateau around 3300 BCE? Analyses of commingled human skeletal remains from the dolmen of Oberbipp

Nowadays, the discovery and excavation of an almost intact Late Neolithic dolmen is rare, as those monuments were often visible in the landscape and have been investigated or destroyed in earlier times; therefore, information about the buried individuals has often been lost. The excavation of the dolmen, a stone grave chamber, from Oberbipp, Switzerland, in 2012 provided a unique opportunity to study human skeletal remains from a Late Neolithic collective burial (3350–2650 BCE). Over 2,000 fragmented and commingled skeletal elements were recovered and form the basis of this morphological study. Established morphological methods were employed to evaluate the minimum number of individuals, age at death, sex, stature, and the presence of pathological alterations and trauma. Sex was determined additionally by aDNA analysis. Elements of the entire human skeleton were recovered indicating a primary burial site. At least 42 individuals (femora) from all age classes (57%:43% adults to subadults) were buried in the dolmen. Based on aDNA analysis (n = 23, partes petrosae) slightly more males than females (44%:35% males to females, 22% indeterminate) were recovered. Stature was estimated from complete femora (n = 3) indicating an average body height between 154–157 cm. Pathological alterations and trauma could be observed on several bones, however, without indications for major interpersonal violence. The caries intensity of Swiss samples seems to be higher compared with other Neolithic European sites. A possible separation of burial areas for males and females based on the recovery of skeletal elements within the dolmen along with aDNA results is postulated. In addition, this article contributes to a better understanding of Late Neolithic populations in Central Europe