A Competing Hydrogen Bonding Pattern to Yield Thermo-Thickening Supramolecular Polymer

International audienceIntroduction of competing interactions in the design of a supramolecular polymer (SP) creates pathway complexity. Ester–bis‐ureas contain both a strong bis‐urea sticker that is responsible for the build‐up of long rod‐like objects by hydrogen bonding and ester groups that can interfere with this main pattern in a subtle way. Spectroscopic (FTIR and CD), calorimetric (DSC), and scattering (SANS) techniques show that such ester–bis‐ureas self‐assemble into three competing rod‐like SPs. The previously unreported low‐temperature SP is stabilized by hydrogen bonds between the interfering ester groups and the urea moieties. It also features a weak macroscopic alignment of the rods. The other structures form isotropic dispersions of rods stabilized by the more classical urea‐urea hydrogen bonding pattern. The transition from the low‐temperature structure to the next occurs reversibly by heating and is accompanied by an increase in viscosity, a rare feature for solutions in hydrocarbons

Trade unions and workplace organization: regulating labour markets in the Belgian and American flat glass industry and in the Amsterdam diamond industry in the nineteenth and early twentieth centuries

In all three industries, internal subcontracting as a way to organize the workplace determined the emergence of craft unionism in the nineteenth century. In both Belgian and American window-glassmaking craft unionism, originally based on exclusion of low-skilled workers who had been underhands in the system of subcontracting, persisted well into the twentieth century, until full mechanization made artisanal glassblowing obsolete. Only then all workers could be united in an industrial union. In diamond manufacturing, craft unions were replaced by a unified industrial union already in the 1890s. In all three industries, trade unions had the biggest impact when they were able to regulate product markets and industrial competition through labour market control. Methods, time frames and duration of labour market control differed considerably, however