Premium
Solid state complexes of poly(L‐lysine) with metal chlorides from the 1st row of the d‐block
Author(s) -
Belfiore Laurence A.,
McCurdie Mary Pat
Publication year - 2000
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.11203
Subject(s) - nickel , hydrobromide , amide , chloride , infrared spectroscopy , transition metal , cobalt , differential scanning calorimetry , ligand (biochemistry) , inorganic chemistry , terephthaloyl chloride , spectrochemical series , crystallography , materials science , chemistry , polymer chemistry , polymer , ligand field theory , organic chemistry , condensation polymer , ion , biochemistry , physics , receptor , thermodynamics , catalysis
Solid state characterization of poly(L‐lysine)hydrobromide was obtained via differential scanning calorimetry, thermogravimetric analysis, optical microscopy and infrared spectroscopy. The glass transition temperature of poly(L‐lysine)hydrobromide is 178°C. This thermal transition has not been reported previously. Poly(L‐lysine)'s T g decreases when complexes are produced with the following divalent transition metal chlorides; cobalt chloride hexahydrate, nickel chloride hexahydrate, copper chloride dihydrate and anhydrous zinc chloride. At 10 mol% salt, nickel, chloride decreases T g by 45°C, and the general trend is Ni 2+ Co 2+ Zn 2+ Cu 2+ . The depression of poly(L‐lysine)'s T g correlates well with ligand field stabilization energies for pseudo‐octahedral and pseudo‐tetrahedral d n complexes (n = 7, 8, 10) from the 1 st row of the d‐block. However, d 9 copper(II) complexes cannot be included in this empirical correlation. Infrared spectroscopic evidence suggests that Co 2+ , Ni 2+ and Zn 2+ coordinate to the carbonyl oxygen in the main chain of the polymer. When transition metal ions coordinate to CO, the network of hydrogen bonded amide groups is disrupted, which lowers the glass transition. The amide I region of the infrared spectrum reveals a hydrogen bonded CO stretch @ 1655 cm −1 that is characteristic of poly(α‐amino acid) random coil conformations, and a metal‐ligand coordinated CO stretch @ 1625 cm −1 in complexes with divalent cobalt, nickel and zinc. The amide II region of the infrared spectrum near 1550 cm −1 is also sensitive to the formation of coordination complexes with these d‐block metal chlorides.