Nanoscale calorimetry of isolated polyethylene single crystals

Abstract

ABSTRACT:We used thin-film differential scanning calorimetry to investigate the melting of isolated polyethylene single crystals with lamellar thicknesses of 12 Ϯ 1 nm. We observed the melting of as few as 25 crystals. Over a wide number of crystals (25-2000 crystals), the heat of fusion was 40% larger than the bulk value. The melting temperature of the isolated single crystals was 123 Ϯ 2°C, 9°C lower than that of the bulk material. We also measured the heat of fusion of quenched crystals (Ϯ15%) over a wide range of heating rates (20,000 -100,000 K/s). Annealing the quenched crystals resulted in shifts in the endotherm peak by as much as 15°C.

Scanning Nanocalorimetry at High Cooling Rate of Isotactic Polypropylene

“…25 Recently developed quasi-adiabatic nanocalorimeters can operate at very high heating rates [26][27][28][29] because of very small addenda and sample heat capacities. Cooling rate, which is not controlled for the quasi adiabatic systems, is limited by total heat capacity, sample size, and heat losses.…”

Annealing of Single Lamella Nanoparticles of Polyethylene

“…12 Thus, crystals of PE with a thickness of about 10 -15 nm and lateral dimensions of the order of 100 nm to a few µm can be generated by crystallization from a highly dilute solution. [13][14][15] These crystals can be used to study the lamellar thickening of the semi-crystalline PE upon annealing. The morphological changes involved in these processes can be easily studied using atomic force microscopy.…”

The design and operation of a mems differential scanning nanocalorimeter for high-speed heat capacity measurements of ultrathin films

“…5. Contact mode atomic force microscopy has been used to measure the roughness and dimensions of polymer crystals directly on the working part of the heater without rupturing the membrane [21]. Focused ellipsometry [22] has been used to measure the thickness of spin-cast polymer films on a Pt heater.…”

“…Also, material characteristics which can be measured (e.g. heat capacity of a sample as a function of temperature, latent heat of a transformation, melting temperature, glass transition temperature) along with selected applications on ultrathin metal films and particles [7], [19], liquids [20], spin-coated films and isolated polymer crystals [21], [22] will be briefly discussed in order to demonstrate the utility of this method.…”