Thermotropic mesomorphism of selected (2-hydroxypropyl)cellulose derivatives

Abstract

ABSTRACT:The thermotropic mesomorphism of some cellulose derivatives (CD) based on the (2-hydroxypropyl)cellulose (HPC) was investigated. Three types of derivatives: two esters (PPC, HxPC) and cyanoethyl derivative (CEPC) were prepared. The X-ray diffraction patterns of CDs were compared with the differential scanning calorimetry, thermooptical, and mechanical measurements within a broad range of the temperature. Two relaxation processes ␣ a and ␣ m , observed in the solid state of HPC, are also exhibited by all CDs, however, at lower temperatures. The ␣ m relaxations, which indicate the transition from frozen anisotropic phase to mobile liquid crystalline (LC)-phase, are shifted towards the lower temperatures with a corresponding increase in the d-spacing of the poly(saccharide) main chains of CDs (as seen in the X-ray measurements). The transition temperature to isotropic phase T ni as well as glass transition temperature T g (␣ a -relaxation) of the investigated CDs depend on the interactions between the lipophilic side chains and the hydrophilic poly(saccharide) main chains of CDs. These interactions are determined by the length and polarity of the lipophilic side chains. The observed changes in the transition temperature to isotropic phase T ni for CDs is consistent with the assumption that LC-organization of the poly(saccharide) main chains is stabilized by the lipophilic side-chains system. A significant increase in the length of the lipophilic side chains leads to nonlinear conformation, thus reducing the influence of van der Vaals forces, and consequently lowering T ni . The polymer with high polarity lipophilic side chains (CEPC) exhibits higher T ni in comparison to the ester derivative PPC with the same length of the side chains but having lower polarity. The stabilization effect of the lipophilic side-chains system on the LC-organization of the poly(saccharide) main chains is determined by the dynamic balance between length and polarity of the lipophilic side-chains system.

Cellulosic nanocomposite membranes from hydroxypropyl cellulose reinforced by cellulose nanocrystals

“…The pure HPC membrane shows two characteristic, diffuse and ambiguous peaks at 2h values of 8.6°and 20.4° ( Fig. 3e), in accordance with results published by Halamus et al (2008) and Wojciechowski (2000). Specifically, the broad diffraction band around 2h = 20.4°is related to slightly ordered amorphous phase of HPC, and the narrow diffraction band observed around 2h = 8.6°is attributed to the backbone-backbone d-spacing of the poly(saccharide) main chains in the crystalline phase of HPC, the intensity of which decreases with increasing CNCs content.…”

Synthesis and characterization of (hydroxypropyl)cellulose/TiO2 nanocomposite films

“…For HPC in the bulk, the intensity diffraction band for 2u ¼ 9.28 exceeds the intensity diffraction band for 2u ¼ 19.7. 3,13 The X-ray diffraction pattern of HPC/TiO 2 nanocomposite suggests the influence of TiO 2 nanoparticles on the amount of the mesomorphic phase of HPC.…”

“…HPC shows the glass transition temperature at þ158C and the isotropization temperature at 2008C. 13 Whereas HPC/TiO 2 nanocomposite shows a similar transition temperature to the isotropic phase the glass transition temperature is shifted to a lower temperature largely below 08C. In the literature, it is supposed that the shift of glass transition temperature of the nanocomposite is related to the packing density of the polymer chain in the polymer-nanoparticle interface.…”

Synthesis and properties of amino acid esters of hydroxypropyl cellulose

“…Esterification is one of the facile means to exploit the hydroxy groups present in cellulose derivatives, and has been the most commonly used synthetic approach leading towards the preparation of cellulose‐based materials capable of exhibiting cholesteric LC phase transitions 31–38. Although the amino acid‐containing polymers have engrossed substantial prominence as a new class of bioactive polymeric materials,11–30 no significant research endeavor concerning the amino acid functionalization of cellulose derivatives has been reported so far.…”