On the macromolecular dynamics of poly(dimethylamino)ethyl methacrylate in aqueous solution and its complex with polyacrylic acid.

This project explored the aqueous solution dynamics of the polydimethylaminoethyl
methacrylate (PDMAEMA) and polyacrylic acid (PAA) systems using fluorescence
spectroscopy techniques.
PDMAEMA and PAA were synthesised several times using free radical polymerisation
techniques with different fluorophore labels included in synthesis. The resulting polymers
were explored with a selection of fluorescence techniques including time resolved anisotropy
measurements, fluorescence decay lifetimes and steady state fluorescence studies.
Initial solution dynamics of these polymer systems indicate that the PDMAEMA exhibits a
tightly coiled structure at high pH values and adopts an uncoiled conformation at low pH
values. PAA exhibits a loose coil conformation at particularly low pH values but adopts an
open extended conformation from around pH 4.5. The study also shows that the amine groups
within PDMAEMA can affect the fluorescence of labels within the polymer.
Studies of the polymer samples in the presence of salts show that even small amounts of salts
added to either system elicits a change in the polymer systems and these are generally most
prominently shown to increase with small salt concentrations, with concentrations of over 1M
often having a much lesser effect. It can generally be seen that the addition of salt to either
system promotes the coiling of the polymer. In the case of PAA this is a much tighter coil and
in PDMAEMA a lowering of the pH at which the polymer exhibits coiling is seen.
Studies of systems made up of both polymers show complicated behaviour in the systems
with the main effects being shown when the pH of the system is such that one or the other
polymer system is ionised and acting in a similar manner to that of the salts.