The treatment of deproteinized natural rubber (DPNR) latex with phospholipases A2, B, C, and D decreased significantly the long-chain fatty acid ester contents in DPNR also molecular weight Higgins' k' constant, except for phospholipase treatment. This indicates presence phospholipid molecules NR, which combine together. Transesterification resulted decomposition functional group at terminal chain-end (α-terminal), including phospholipids formed linear molecules. addition small amounts...

Classification of tea quality is now mainly performed according to the sensory results by professional tasters. However, this evaluation method inconsistent in differentiating their qualities. A combination a 1H NMR technique and multivariate analysis was introduced green means metabolomic technique. broad range metabolites were detected spectrometry. The principal component (PCA) used reduce complexity spectra data set provided discrimination result. It offered an extensive clue for...

Deproteinized natural rubber latex (DPNR-latex) was treated with lipase and phosphatase in order to analyze the structure of chain-end group (α-terminal). The enzymatic treatment decreased content long-chain fatty acid ester groups DPNR from about 6 2 mol per molecule. molecular weight intrinsic viscosity were reduced one-third after phosphatase. Huggins' k' constant enzyme-treated showed formation linear molecules. distribution changed apparently 1H NMR spectrum obtained DPNR-latex small...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHaloaldehyde polymers. 51. Helix-sense reversal of isotactic chloral oligomers in solutionKoichi Ute, Katsuo Hirose, Hiroaki Kashimoto, Koichi Hatada, and Otto VoglCite this: J. Am. Chem. Soc. 1991, 113, 16, 6305–6306Publication Date (Print):July 1, 1991Publication History Published online1 May 2002Published inissue 1 July 1991https://pubs.acs.org/doi/10.1021/ja00016a076https://doi.org/10.1021/ja00016a076research-articleACS PublicationsRequest...

Stereoregular isotactic and syndiotactic poly(methyl methacrylate)s (it- st-PMMAs) are known to form a multiple-stranded complementary helix, so-called stereocomplex (SC) through van der Waals interactions, which is rare example of helical supramolecular structures formed by commodity polymer. In this study, we prepared SCs using uniform it- st-PMMAs those with narrow molecular weight distribution having different weights investigated their in detail high-resolution atomic force microscopy...

Liquid chromatography at the critical adsorption point (LC CAP) with on-line NMR detection (on-line LC CAP NMR) was utilized for analysis of tacticity distribution stereo-regular poly(ethyl methacrylate)s (PEMAs). The separation a model PEMA sample composed four constituents similar molar masses (Mw = (14-16) x 10(3) g mol-1) differing in their (rr triad content 0, 33, 68, and 89%) achieved by mixed eluent acetone, acetone-d6, cyclohexane. composition within each peak eluted from column...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDirect formation of the helical polymer conformation in stereospecific synthesis: x-ray crystallographic determination linear chloral oligomersOtto Vogl, Fu Xi, Frantisek Vass, Koichi Ute, Tohru Nishimura, and HatadaCite this: Macromolecules 1989, 22, 12, 4658–4660Publication Date (Print):December 1, 1989Publication History Published online1 May 2002Published inissue 1 December...

Abstract The structure of both terminal units and alignment the isoprene give conclusive evidence for initiation termination mechanisms rubber formation in fungi. As shown Figure 4, polymerization is estimated to start from trans, trans-farnesyl pyrophosphate proceeds by successive condensation IPP form cis configuration. presumed occur direct esterification polyisoprenyl (PIP-PP) or dephosphorylation PIP-PP followed with fatty acids. It remarkable that hydroxyl group corresponding...

Alkali metal cations, including the Li⁺cation, have been proposed to play a dual role in radical polymerization of<italic>N</italic>,<italic>N</italic>-dimethylacrylamide.

Abstract The chemical structures of natural rubber (NR) end groups are investigated by combining treatments and sensitivity‐enhanced modern nuclear magnetic resonance (NMR) spectroscopy instruments equipped with a cryoprobe. obtained 1 H NMR spectrum the α‐end has improved signal intensity than that conventional instruments, as well clearer splitting patterns due to higher resolution given field. Through H/ 13 C 2D experiments 1D spectra model compounds, four types suggested. Two among them...

The physical properties of poly(lactic acid) (PLA) are influenced by its stereoregularity and stereosequence distribution, polymer stereochemistry can be effectively studied NMR spectroscopy. In previously published studies PLA tacticity, the data were fitted to pair-addition Bernoullian models. this work, we prepared several samples with a tin catalyst at different L,L-lactide D,D-lactide ratios. Upon analysis tetrad intensities model, found substantial deviations between observed...