Synthesis of Network Biobased Aliphatic Polyesters Exhibiting Better Tensile Properties than the Linear Polymers by ADMET Polymerization in the Presence of Glycerol Tris(undec-10-enoate).

Development of biobased aliphatic polyesters with better mechanical (tensile) properties in film has attracted considerable attention. This report presents the synthesis of soluble network biobased aliphatic polyesters by acyclic diene metathesis (ADMET) polymerization of bis(undec-10-enyl)isosorbide diester [M1, dianhydro-D-glucityl bis(undec-10-enoate)] in the presence of a tri-arm crosslinker [CL, glycerol tris(undec-10-enoate)] using a ruthenium-carbene catalyst, and subsequent olefin hydrogenation using RhCl(PPh3)3. The resultant polymers, after hydrogenation (expressed as HCP1) and prepared in the presence of 1.0 mol% CL, showed better tensile properties than the linear polymer (HP1) with similar molecular weight [tensile strength (elongation at break): 20.8 MPa (282%) in HP1 vs. 35.4 MPa (572%) in HCP1]. It turned out that the polymer films prepared by the addition of CL during the polymerization (expressed as a 2-step approach) showed better tensile properties. The resultant polymer film also shows better tensile properties than the conventional polyolefins such as linear high density polyethylene, polypropylene, and low density polyethylene.

Synthesis of High Molecular Weight Biobased Aliphatic Polyesters Exhibiting Tensile Properties Beyond Polyethylene.

Synthesis of high molecular weight polyesters prepared by acyclic diene metathesis (ADMET) polymerization of bis(undec-10-enoate) with isosorbide (M1), isomannide (M2), and 1,3-propanediol (M3) and the subsequent hydrogenation have been achieved by using a molybdenum-alkylidene catalyst. The resultant polymers (P1) prepared by the ADMET polymerization of M1 (in toluene at 25 °C) possessed high Mn values (Mn = 44400-49400 g/mol), and no significant differences in the Mn values and the PDI (Mw/Mn) values were observed in the samples after the hydrogenation. Both the tensile strength and the elongation at break in the hydrogenated polymers from M1 (HP1) increased upon increasing the molar mass, and the sample with an Mn value of 48200 exhibited better tensile properties (tensile strength of 39.7 MPa, elongation at break of 436%) than conventional polyethylene, polypropylene, as well as polyester containing C18 alkyl chains. The tensile properties were affected by the diol segment employed, whereas HP2 showed a similar property to HP1.

Estimating health risk from exposure to 1,4-dioxane in Japan.

Exposure to 1,4-dioxane from the atmosphere around high-emission plants and from consumer products used in daily life that contain the substance may have adverse health effects; however, its emission into the atmosphere is not regulated. In this study, the health risk posed by 1,4-dioxane is assessed to investigate whether measures should be undertaken to reduce exposure to 1,4-dioxane. The notion of the margin of exposure (MOE), given by the ratio of no observed adverse effect level (NOAEL) to actual or projected exposure level, is used to assess risk. In exposure assessment, two types of exposure channel are considered: (a) the use of consumer products that contain 1,4-dioxane and (b) the inhalation of air around high-emission plants. To estimate exposure via channel (a), we measured the concentration of 1,4-dioxane in consumer products and estimated the interindividual variability of exposure by Monte Carlo simulation that reflects the measured data. To estimate exposure via channel (b), we employed a local-level atmospheric dispersion model to estimate the concentration of 1,4-dioxane immediately around high-emission plants. For hazard assessment, we derived the inhalatory and oral NOAELs for liver adenomas and carcinomas and the uncertainty factor. The results suggest that measures are not needed to reduce exposure to 1,4-dioxane from consumer products. As for inhalation exposure around high-emission plants, some residents may be exposed to health risks if certain conservative analytical conditions are assumed. Even in this case, we conclude that it is not necessary for Plant A to stop the use of 1,4-dioxane immediately and that medium- to long-term emission reduction measures should be sufficient.