The Structure of Polycaprolactone-Clay Nanocomposites Investigated by ₁H NMR Relaxometry

Abstract

Nanocomposites based on polycaprolactone (PCL), containing concentrations of 1, 3 and 5 wt% of sodium montmorillonite (NT-25) and organo-modified montmorillonite clay, with three different salts (Viscogel B7, Viscogel S4 and Viscogel B8), were prepared employing the solution intercalation method using chloroform. The PCL nanocomposites were characterized by relaxometry, through determination of the hydrogen spin-lattice relaxation times using low-field nuclear magnetic resonance (NMR). Conventional X-ray diffraction (XDR) was also used to measure the basal space of the nanoclay. The proton spin-lattice relaxation parameters showed that hybrid nanocomposites were formed, containing different parts of intercalated and exfoliated organoclay. The proton T1rhoH also indicated changes in the microstructure, organization and the molecular mobility of the hybrid materials. NMR relaxometry is a good way to evaluate nanomaterials because it provides complementary information, since it is measured in a different time scale. Furthermore, differential scanning calorimetry and thermogravimetric analysis were also used to investigate the crystallization and thermal behavior of the nanocomposites, respectively. All materials had low crystallization temperature (Tc) and the melting temperature (Tm) were very close to that of the PCL matrix, but the degree of crystallinity of the nanocomposites decreased. TGA analysis demonstrated that montmorillonite accelerates PCL's decomposition while unmodified montmorillonite has the opposite effect.

The Development and Characterization of Polycaprolactone and Titanium Dioxide Hybrids

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Development of Polycaprolactone/Poly(Vinyl Alcohol)/Clay Microparticles by Spray Drying

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Development and characterization of hybrid materials based on biodegradable PLA matrix, microcrystalline cellulose and organophilic silica

“…Generally speaking, the decrease in the relaxation parameter is a consequence of an increase in the molecular mobility of chains due to the increase in their freedom [8,[17][18][19] . Changes in the domain curves such as baseline mean that the samples have an amorphous or non-ordered organization, involving a mixture of more than one chain organization [8,19] .…”