Rubbery wound closure adhesives. I. design,synthesis, characterization,and testing of polyisobutylene‐based cyanoacrylate homo‐ and co‐networks

Novel rubbery wound closures containing various proportions and molecular weights of polyisobutylene (PIB) and poly(2‐octyl cyanoacrylate) [P(OctCA)] for potential clinical use were designed, synthesized, characterized, and tested. Homo‐networks were prepared by crosslinking 3‐arm star‐shaped PIBs fitted with terminal cyanoacrylate groups, [Ø(PIB‐CA)₃], and co‐networks by copolymerizing Ø(PIB‐CA)₃ with OctCA using N‐dimethyl‐p‐toluidine (DMT). Neat Ø(PIB‐CA)₃, and Ø(PIB‐CA)₃/OctCA blends, upon contact with initiator, polymerize within seconds to optically transparent strong rubbery co‐networks, Ø(PIB‐CA)₃‐co‐P(OctCA). Homo‐ and co‐network formation was demonstrated by sol/gel studies, and structures and properties were characterized by a battery of techniques. The T_g of P(OctCA) is 58 °C by DSC, and 75 °C by DMTA. Co‐networks comprising 25% Ø(PIB‐CA)₃ (M_n = 2400 g/mol) and 75% P(OctCA) are stronger and more extensible than skin. Short and long term creep studies show co‐networks exhibit high dimensional stability and <6% creep strain at high loading. When deposited on porcine skin co‐networks yield hermetically‐adhering clear rubbery coatings. Strips of porcine skin coated with co‐networks could be stretched and twisted without compromising membrane integrity. The co‐network is nontoxic to L‐929 mouse fibroblasts. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1640–1651     

Walter B. Gratzer (1932–2021) – molecular scientist and science writer

Structural Chemistry - Walter Gratzer (1932–2021) arrived in England as a child refugee from Nazism, without speaking English, and became one of the most successful and influential science...     

On the lack of capillary Mössbauer spectroscopic effect for SnII-containing aqueous solutions trapped in corning Vycor ‘thirsty’ glass

Liquids trapped in the pores of certain silicate glasses (such as Corning Vycor ‘thirsty’ glass) were found to display frozen solutions like behavior at temperatures much higher than their actual freezing point. For example, recoilless γ-resonance absorption was observed for Mössbauer active solutes such as ¹¹⁹Sn and ⁵⁷Fe salts at room temperature (i.e., without the need of quenching). Thus capillary Mössbauer spectroscopy (CMS) proved to be a new and useful experimental tool with great potential in solution chemistry. As part of a research project concerned with the hydrolysis of Sn^II salts, we attempted to perform ¹¹⁹Sn CMS measurements for solutions containing stannous ion in a range of aqueous environments. Somewhat surprisingly, we found that under ambient conditions, Sn^II aqueous liquid solutions, both the acidic and the basic systems, are essentially CMS-silent. This can be attributed to the strong temperature dependence of Lamb–Mössbauer factor of Sn^II species, which may result in the complete disappearance of Mössbauer pattern well below room temperature. These observations can also explain why previous publications concerned with the use of CMS dealt exclusively with Sn^IV and not with Sn^II containing liquids.     

Special issue: honoring George A. Olah at 90

This collection of contributions honors George A. Olah on the occasion of his 90th birthday.     

Alkali Carbonate Effects on N‐(2‐Hydroxyethyl)urea Cyclization: Application to a 2‐Imidazolidinone Scale‐Up

An imidazolidinone intermediate ( 3 ) used in the synthesis of novel HIV‐entry inhibitors was prepared on multihundred gram scales in four steps and 40% overall yield. The penultimate step in the synthesis involved regioselective N‐cyclization of N‐(2‐hydroxylethyl)urea ( 11 ) by in situ activation of the terminal hydroxyl group with p‐TsCl in the presence of base. The ratio of N‐cyclized to O‐cyclized products followed a group IA periodic trend relative to the alkali carbonate base employed. The use of Cs₂CO₃ as base effected the desired N‐cyclization with a high degree of regiocontrol (>98%).     

The Stretching Vibration of Hydroxyl Ions in LaGaO3

The presence of hydroxyl ions in LaGaO₃ single crystals has been detected by means of Fourier Transform Infrared (FTIR) absorption spectroscopy. A single narrow absorption line of the OH^? stretching vibration at about 3521 cm^?1 has been observed at T=9k in most of the as-grown crystals. The vibrational frequency decreased abruptly at the orthorhombic-rhombohedral structural phase transition temperature (T_c=418K). The parameters of the anharmonic potential of the OH^? stretching vibration have been determined from the isotopic replica and the overtone frequency and intensity, and found to be in agreement with those measured for hydroxyl ions in other oxide crystals.