Unveiling thermal transitions of polymers in subnanometre pores

The thermal transitions of confined polymers are important for the application of polymers in molecular scale devices and advanced nanotechnology. However, thermal transitions of ultrathin polymer assemblies confined in subnanometre spaces are poorly understood. In this study, we show that incorporation of polyethylene glycol (PEG) into nanochannels of porous coordination polymers (PCPs) enabled observation of thermal transitions of the chain assemblies by differential scanning calorimetry. The pore size and surface functionality of PCPs can be tailored to study the transition behaviour of confined polymers. The transition temperature of PEG in PCPs was determined by manipulating the pore size and the pore–polymer interactions. It is also striking that the transition temperature of the confined PEG decreased as the molecular weight of PEG increased

Synthesis and characterization of MAPO-11 molecular sieves

In this work MAPO-11 molecular sieve was prepared with several degrees of magnesium substitution. The syntheses were carried by using phosphoric acid, pseudo-boehmite and magnesium acetate as sources of structural elements and diisopropylamine as the structure-directing agent. The samples were characterized by powder X-ray diffraction, thermogravimetry, infrared spectroscopy, solid-state nuclear magnetic resonance, scanning electron microscopy and elemental analysis. The X-ray diffractograms indicate that the AEL structure is obtained free of contaminating phases up to a magnesium molar ratio of 0.3 in the reaction mixture. Higher levels of magnesium cause the formation of other phases. Thermogravimetry, MAS nuclear magnetic resonance of P-31 and infrared spectroscopy confirm the magnesium isomorphous substitution for aluminum up to this magnesium content in the reaction mixture. (C) 2002 Published by Elsevier Science Inc.534169913514