Molecular weight recognition in the multiple-stranded helix of a synthetic polymer without specific monomer-monomer interaction.

Stereoregular isotactic and syndiotactic poly(methyl methacrylate)s (it- and st-PMMAs) are known to form a multiple-stranded complementary helix, so-called stereocomplex (SC) through van der Waals interactions, which is a rare example of helical supramolecular structures formed by a commodity polymer. In this study, we prepared SCs by using uniform it- and st-PMMAs and those with a narrow molecular weight distribution having different molecular weights and investigated their structures in detail using high-resolution atomic force microscopy as a function of the molecular weight and molecular weight distribution of the component PMMAs. We found that complementary it- and st-PMMAs with the longer molecular length determine the total length of the SC, and molecules of the shorter component associate until they fill up or cover the longer component.

Study on blood compatibility with poly(2-methoxyethylacrylate)--relationship between surface structure, water structure, and platelet compatibility in 2-methoxyethylacrylate/2-hydroxyethylmethacrylate diblock copolymer.

Diblock copolymers composed of 2-methoxyethylacrylate (MEA) and 2-hydroxyethylmethacrylate (HEMA) were firstly prepared (the composition ratio = 90/10, 79/21, 66/34, and 48/52 mol/mol) by anion living polymerization. ESCA analysis of their surface structures (dry state) revealed that PMEA segment was segregated to the top surface in all of the polymers, whereas the results of contact angle of water (wet state) showed that the surfaces were covered with PHEMA segment. In vitro platelet adhesion test showed that these polymers had the excellent compatibility with platelet compared to PHEMA homopolymer.

Structural characterization of alpha-terminal group of natural rubber. 2. Decomposition of branch-points by phospholipase and chemical treatments.

The treatment of deproteinized natural rubber (DPNR) latex with phospholipases A(2), B, C, and D decreased significantly the long-chain fatty acid ester contents in DPNR and also the molecular weight and Higgins' k' constant, except for phospholipase D treatment. This indicates the presence of phospholipid molecules in NR, which combine rubber molecules together. Transesterification of DPNR resulted in the decomposition of the functional group at the terminal chain-end (alpha-terminal), including phospholipids and formed linear rubber molecules.

Structural characterization of alpha-terminal group of natural rubber. 1. Decomposition of branch-points by lipase and phosphatase treatments.

Deproteinized natural rubber latex (DPNR-latex) was treated with lipase and phosphatase in order to analyze the structure of the chain-end group (alpha-terminal). The enzymatic treatment decreased the content of long-chain fatty acid ester groups in DPNR from about 6 to 2 mol per rubber molecule. The molecular weight and intrinsic viscosity were reduced to about one-third after treatment with lipase and phosphatase.

Temperature gradient interaction chromatography and MALDI-TOF mass spectrometry analysis of stereoregular poly(ethyl methacrylate)s.

Temperature gradient interaction chromatography (TGIC) was applied for the separation of stereoregular poly(ethyl methacrylate) (PEMA) according to the tacticity. The three PEMA samples with differing tacticity (rr triad content 0, 53, and 91%) prepared by anionic polymerization were used. C18 bonded silica and a mixture of CH2Cl2 and CH3CN (30/70, v/v) were used as stationary and mobile phase, respectively.