Langmuir-Blodgett Monolayers of Carborane-Poly(ethylene glycol) Complexes

Abstract

The carborane (CB) is a cluster composed of boron, carbon and hydrogen atoms. Having rich boron, CB has been recognized for its unique properties and its potential as a boron neutron capture therapy (BNCT) material. When using CB to BNCT, low water solubility is disadvantage. Solubility problem can be solved by connecting each CB with polyethylene glycol (PEG). This study used three different molecular weights of PEG (Mwt. 3800, 5010 and 6000). CB-PEG complexes at the air-water interface and Langmuir-Blodgett (LB) films of CB-PEG complexes were investigated by using surface pressure (Π)-surface area (A) isotherm, hysteresis and atomic force microscope (AFM). Surface pressure (Π)-surface area (A) isotherms show that CB-PEG complexes have different limiting area according to the molecular weight of PEG. The AFM images also show the close-packed arrangement for the higher molecular weights of PEG. CB-PEG complexes make dot domains at the low pressure. As the surface pressure increases, the domains are aggregated and make large domains. To investigate the effect of salt, 0.5 M NaCl solution was used as a subphase and used pressure (Π)-surface area (A) isotherm and hysteresis. As a result, there was no change at the low pressure and the surface area was increased as the pressure was increased.