Synthesis of end-capped polyester from SmI2-catalyzed Tishchenko-type polyaddition of dialdehydes

SmI₂-catalyzed polyaddition of 1,12-dodecanedial followed by treatment with benzaldehyde gives a polyester (1) containing three structural units, [OCH₂-(CH₂)₁₀-CH₂O], [OCH₂-(CH₂)₁₀-CO], and [CO-(CH₂)₁₀-CO], in the main chain and an OCH₂Ph end-capping group. GPC analysis of 1 shows molecular weights of M_n = 5.5 × 10³ and M_w = 14 × 10³. The ¹H-NMR spectrum reveals the polymer structure with the COOCH₂Ph end group as well as the M_n value (2.6 × 10³) calculated based on an amount of the end-capping group and lower than that estimated from GPC. Mixtures of terephthalaldehyde and 1,12-dodecanedial in several molar ratios undergo similar polyaddition catalyzed by SmI₂ to give the corresponding copolyesters after treatment with benzaldehyde. Increase in the ratio of 1,12-dodecanedial causes increase in yield and molecular weight of the copolymer. Terephthalaldehyde shows a tendency to give alcohol-side —O—R—O— unit in the polyester, whereas 1,12-dodecanedial is mostly incorporated as the acid-side —CO—R′—CO— unit. Terminal aldehyde group derived from dodecanedial is capped effectively by benzaldehyde to give the COOCH₂Ph end group. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2821–2825, 1997     

Development of a new density functional program for all-electron calculation of proteins

In this article, we propose a new molecular orbital program for all-electron calculation of proteins which is based on density functional theory. To carry it out in a fully analytical way, we adopted the (pure-) analytical Xα method and modified it for saving a lot of memories for large-scale calculations. The recent software technology sophisticated in information science is inevitably applied to achieve calculations of large molecular systems. The program is coded by the object-oriented language C + +, its output is shown graphically, and the most of the procedures in this program are controlled through an efficient graphical user interface developed by ourselves. Such technology supports the safe construction of the huge software, the tidy representation of enormous data, and the ready control of complex calculations. Test calculations with various sizes of glycine polypeptides indicate that the computation time is proportional to the 1.7 powers of the number of residues. This result suggests that the all-electron calculations of proteins consisting of over 1000 atoms could be performed with distributed and/or massively parallel computers. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 245–256, 1997     

Potential of two-dimensional near-infrared correlation spectroscopy in studies of pre-melting behavior of nylon 12

This review paper discusses the potential of generalized two-dimensional (2D) near-infrared (NIR) correlation spectroscopy in studies of pre-melting behavior and hydrogen bonds of nylon 12. A 2D NIR study on dissociation and hydrogen bonds of N-methylacetamide (NMA) is also reviewed here as a model compound study of nylon 12. Fourier transform (FT)-NIR spectra in the region of 9000–5000 cm⁻¹ of nylon 12 were measured over a temperature range of 30–150°C where gradual weakening of inter- or intramolecular associative interactions and decrease of local order leading to the eventual fusion of nylon 12 crystals are observed. The 2D correlation analysis provided the following conclusions for the pre-melting behavior of nylon 12. (i) There are at least eight bands in the 6800–6100 cm⁻¹ region assignable to free- and hydrogen-bonded NH groups of nylon 12 in various environments. The asynchronous 2D correlation spectrum in the above region indicates that the amide groups with free carbonyl oxygen appear first and then the unassociated free amide and amide groups with free NH follow as the temperature is increased. (ii) The asynchronous spectrum in the 6000–5500 cm⁻¹ region, where the first overtones of the CH₂ stretching modes are expected to appear, indicates that substantial amount of disordered or dissociated components start appearing before the disappearance of more ordered components. It seems that they appear as the pre-melting precursors (or even possibly as the indirect cause) to the precipitous decrease of the ordered components associated with melting of nylon 12 occurring at a much higher temperature.     

Helix change of polypeptides in the solid state as studied by NMR spectroscopy

The conformational characterization of solid polypeptides has been carried out by means of high-resolution solid-state NMR. It has been demonstrated that high-resolution solid-state NMR spectroscopy is a very useful means for elucidating the structure of polypeptides and proteins in the solid state.     

Hydration Changes during Thermosensitive Association of a Block Copolymer Consisting of LCST and UCST Blocks

Summary: Thermosensitive association of a diblock copolymer consisting of poly(3‐dimethyl(methacryloyloxyethyl) ammonium propane sulfonate) (PdMMAEAPS), as an upper critical solution temperature (UCST) block, and poly(N,N‐diethylacrylamide) (PdEA), as a lower critical solution temperature (LCST) block, has been investigated by using IR spectroscopy. The ν(CO) and ν(SO) bands of the PdMMAEAPS block and the amide I band of PdEA block critically changed at the UCST and LCST, respectively, indicating that the segmental interaction of each block is altered at each transition.

The double temperature responsiveness of a UCST block and LCST block containing diblock copolymer. Micelles form at temperatures both below the UCST and above the LCST of the blocks.