solution where high concentration is necessary, either the J The aggregation of a long-chain thiacarbocyanine dye (5,5or H aggregate can be formed at very lower concentrations dichloro-3,3-dioctadecyl-9-ethylthiacarbocyanine perchlorate) in in the presence of small amount of polyelectrolytes (13monolayers on a subphase containing heparin has been investi-16). Such effect of polyelectrolytes is not limited to the gated as a function of surface pressure by in situ measurement of solution. Addition of some polyelectrolytes into the subphase the absorption spectra. Only the monomer band was observed at can also alter the properties of charged amphiphilic monolower surface pressure, while two J aggregate bands at 648 and layers through polyion complex formation (17-19). Pre-666 nm were observed when the surface pressure was above 25 viously, we have found that presence of synthetic polyanions mN m 01 . Their intensities increased with the surface pressure.
containing SO 3 0 or COO 0 such as poly(acrylic acid, sodium
The H aggregate was observed at higher surface pressure (50 mN m 01 ). Repeated expansion and compression of the monolayer on salt) (PAA), poly(styrenesulfonic acid, sodium salt) the heparin subphase can increase the relative amount of the H (PSS), and poly(vinyl sulfonic acid, potassium salt) (PVS) aggregates. The spectral changes in the monolayers show that in the subphase can greatly influence the aggregation of a there are reversible and irreversible processes in the compression long-chain thiacarbocyanine dye in the monolayer states and expansion cycles. In LB films, the J aggregate was formed (20). In this paper we report the effect of heparin, a naturally even at lower surface pressure. Only the J band at 650 nm is occurring polyanion that contains both SO 3 0 and COO 0 observed in the LB films.