Molecular Interactions of Poly (methylmethacrylate), Poly (vinyl alcohol), Poly(ethylene glycol), Chitosan, Cellulose and Starch Polymers with Iodine

Abstract

The interactions betweenpoly(methylmethacrylate)(PMMA),poly(vinylalcohol) (PVA) poly(ethylene
glycol)(PEG)as industrial biopolymers andchitosan, cellulose, starch as natural biopolymers with iodine(I2)
were investigated using diethyl ether as a solvent. 5% of I2 was added to each polymer and soaked in the
solvent. The interactions were investigated using concepts of the activation energy(Ea), Decisivefactor (Df)
and the changing in the glass transition temperature (?Tg,
s). Therefore, the differential scanning calorimeter
(DSC) was used to monitorthe thermal transitions. The optical microscope(OM) device was used to study
the surface morphologies.Resultsshowed a clear depression in the glass transition temperatures (Tg
,
s) for all
polymers( as well as new colors appear) except cellulose still unaffected .It appears that cellulose molecules
coated with a film prevent iodine to diffuse through the network structure of cellulose thus no effected its
color or its Tg which indicates that molecular structure of cellulose quite different from that of starch and for
this fact cellulose not soluble by a solvent and undigested in the human body. The depression inTg values
of polymers indicate that iodine ruptures the engineering bonds of the polymers. The most effected Tg is of
chitosan (lowered by 40.23?C, this mean that iodine ruptures both hydrogen bonding through nitrogen and
oxygen atoms in chitosan molecule.
From Tg values, it seems that iodine can acts as moderate plasticizer, by diffusing through the net of synthetic
and natural biopolymers ruptures their secondary bonds result in depression of their Tg except in case of
cellulose.
The order of Tg depression is:
Chitosan (40.23)>PMMA (27.89)>starch (22.29)>PVA (13.89) >PEG (5.78)>cellulose (0)
Which showed no distinguish between natural and synthetic biopolymers.
From Tg values calculation of the energy given by the addition of iodine to the polymers was done and
shown the following order:
chitosan(27.394)>PMMA(18.442) =starch(18.414)>PVA(9.316 )>PEG(4.315)>cellulose( 0 )