0 bar for 10 min. Rheological measurements had been carried out on a strain-controlled rheometer (ARES, TA Instruments Inc.?Waters LLC) applying a 25 mm parallel plate geometry. The rheometer was equipped having a convection oven under compressed air to handle the temperature. Sample characterization was carried out by dynamic temperature ramp tests (temperature ranging from 808C to 2008C at 108C min21, frequency ?0.five rad s21 and strain ?0.five ) and frequency sweep tests (frequency range ?0.1?one hundred rad s21 and strain ?0.five , at 1658C). Time sweep tests have been also performed, to study polymer stability for the duration of the tests (frequency ?0.5 rad s21 and strain ?0.five , at 1658C for 30 min). A value of strain was chosen to be able to have a torque within the sensitivity of your instrument in the linear viscoelastic region.2.2.four. Thermal characterizationThermal characterization was performed by DSC and TGA on specimens of PU films prepared by compression moulding, as previously described (see ?.Price of Ethyl 5-bromo-2-methylnicotinate two.3).2.2.4.1. Differential scanning calorimetryDSC was performed employing a TA Instruments DSC Q20. Every single sample (weighing approx. 5 mg) was encapsulated within a hermetic aluminium pan prior to evaluation. The sample was then heated from 208C to 2008C at 108C min21 (initially heating scan), isothermally maintained at 2008C for 3 min, cooled to 2608C at 108C min21 (cooling scan), isothermally maintained at 2608C for three min and reheated from 2608C to 2008C at 108C min21 (second heating scan) beneath nitrogen. All thermograms were analysed applying the TA UNIVERSAL Analysis software program. Melting temperature (Tm) was measured because the melting peak temperature, although melting enthalpy (DHm) was calculated via linear integration of the endothermic melting peak. The glass transition temperature (Tg) was measured as the midpoint temperature with the transition step (i.e. temperature at half step height). The crystallization temperature (Tc) was measured because the crystallization peak temperature, while crystallization enthalpy (DHc) was calculated via linear integration of the exothermic crystallization peak.Formula of 5-Bromo-2-(tert-butyl)pyridine An further thermal characterization of PU was carried out that was aimed at reproducing the temperature ramp test performed throughout the non-isothermal rheological analysis: PU samples had been quickly heated from space temperature to 808C, isothermally kept at 808C for ten min and after that heated from 808C to 2008C at 108C min21.2. Material and methods2.1. Polyurethane synthesisA PU was synthesized from poly(1-caprolactone) (PCL) diol (Across Organics, Mn ?2000 Da), 1,4-butandiisocyanate (BDI) (AlloraChem) and L-lysine ethyl ester dihydrochloride (SigmaAldrich) chain extender, based on a previously described system [11,13].PMID:27217159 Differently from that procedure, the 1,2-dichloroethane solvent (Sigma-Aldrich) was dried over activated ?molecular sieves (Carlo Erba Reagents, four A) below a nitrogen atmosphere for 48 h before use. Furthermore, a further polymer purification step was introduced: the vacuum-dried polymer was milled at a grain size of 0.75 mm and washed with methanol (15 ml g21). The obtained powder was lastly dried under vacuum at 408C for 72 h.2.2.four.two. Thermogravimetric analysisThe thermogravimetric and derivative thermogravimetric curves were recorded on a TA Instruments TGA Q500. PU samples wereweighed (initial weight of approx. 15 mg) in an alumina crucible and heated beneath air to a temperature array of 50?008C at a heating rate of 108C min21 (non-isothermal TGA). Isothermal TGA was also performed: t.