Mesoporous methylecellulose for controlled hormone and fertilizer release

Abstract

The present study deals with the controlled release of urea (a fertilizer) and gibberellic acid (a growth hormone) from beads and mesoporous methylcellulose films derived from methylcellulose gels. The calorimetric and morphological investigation of the thermogelation of methylcellulose gels in N, Ndimethylformamide (DMF) and the new coil-helix-bead-rod model is presented. The optical microscopy studies reveal the presence of loosely bound beads of MC with DMF at a lower concentration. These beads get interconnected to rods and subsequently, a continuous thick gel is formed on increasing the concentration. The thermoreversible gelation of MC in DMF is studied with the coil-helix model. The new intermediates called beads and rods are introduced in the coil-helix model. In this new coil-helix-bead-rod system, the random coils first form helix on cooling and these helixes further aggregate into beads and rods. The minimum number of beads for gelation to occur is around 89.86 in a unit chain of MC. The actual rod length is always greater than that of the size of a bead (2.5 μm). The gel-sol transition of MC-DMF gel (3 wt % MC-88000) may be divided into two parts, first ranging from 71 oC to 92.9 oC and the second ranges from 91.9 oC t 107.5 oC. The main peak at 75.6 oC may be defined as primary peak and the shoulder at 91.9 oC is defined as secondary peak. The primary peak indicates the disintegration of strongly associated rods into weakly associated beads and the secondary peak indicates the disintegration of beads into a solution state. The rheological behavior of the gels of methylcellulose (MC) in N, N dimethylformamide (DMF) are studied under dynamic compression with respect to the presence of various concentrations (1, 2, 2.5 and 3 wt %) and different MW (MC-41,000, MC-63,000 and MC 88,000) of MC in the gels. The effect of highly substituted cationic (Cetyl trimethyl ammonium bromide, CTAB), less substituted cationic (hexadodecyl ammonium bromide, HDAB), CTAB and HDAB modified montmorillonite (K-10) clay (nanofillers) (CTABMONT and HDABMONT) and non-ionic surfactants on the rheological properties of methylcellulose (MC) DMF gels are also studied. The storage modulus of the MC-MDF gels increases with an increase in frequency. During the frequency scan, the storage and loss modulus of MC-DMF gel crosses over each other at two different frequencies.