Identification of optically clear regions of ternary polymer blends using a novel rapid screening method

Abstract

The application of a rapid screening method for the construction of ternary phase diagrams is described for the first time, providing detailed visualization of phase boundaries in solvent-mediated blends. Our new approach rapidly identifies ternary blend compositions that afford optically clear materials, useful for applications where transparent films are necessary. The use of 96well plates and a scanning plate reader has enabled rapid optical characterization to be carried out by transmission spectrophotometry (450 nm), whilst the nature and extent of crystallinity was examined subsequently by wide angle X-ray scattering (WAXS). The moderating effect of cellulose acetate butyrate can be visualized as driving the position of the phase boundaries in poly(Llactic acid)/polycaprolactone (PLLA/PCL) blends. More surprisingly, the boundaries are critically dependent on the molecular weight of the crystallizable PLLA and PCL, with higher molecular weight polymers leading to blends with reduced phase separation. On the other hand, the propensity to crystallize was more evident in shorter chains. WAXS provides a convenient way of characterizing the contribution of the individual blend components to the crystalline regions across the range of blend compositions.

Ternary polymer blends based on poly(lactic acid): Effect of stereo‐regularity and molecular weight

“…In our previous work, we concluded that the nature of the non‐transparent regions is influenced by crystallization . Therefore, in this work the study of the nature and extent of crystallinity from the different stereo‐regularity of PLA blends was further observed by XRD.…”

“…In our previous work, we concluded that the nature of the nontransparent regions is influenced by crystallization. 18 Therefore, in this work the study of the nature and extent of crystallinity from the different stereo-regularity of PLA blends was further observed by XRD. Table IV shows the values of X-ray incidence angle (2h) and lattice inter-planar spacing of the crystal (d-spacing) of the homopolymers as observed by the XRD technique.…”

“…This technique is a combinatorial approach using transmission spectrophotometry, 96‐well plates, and a multi‐wavelength plate reader. It has permitted the phase diagrams to be mapped out to identify the optically clear, apparently miscible regions in our binary and ternary solvent blends …”

“…It has permitted the phase diagrams to be mapped out to identify the optically clear, apparently miscible regions in our binary and ternary solvent blends. 18 About 7 wt % solutions of individual polymers are dissolved in chloroform (used as the solvent) and then pipetted into the 96wells with the desired compositions. Samples were left to evaporate slowly at 21 C (6 2 C) for 24 h, followed by drying in vacuum at 40 C for 24 h to remove residual solvent, this produced films with a thickness of approximately 100 lm.…”

“…An important point to note is that the effect of stereo‐regularity of PLA studied in binary blends are considerably represented in the literature; however, three component blends appear significantly less frequent and are not yet fully understood. In previous work, we investigated optical clarity of novel ternary blends of PLLA/polycaprolactone (PCL)/cellulose acetate butyrate (CAB) these blends improved the properties of PLLA by interactions between polymer pairs (i.e., PLLA/CAB, PCL/CAB) . Although, optical clarity is not an absolute predictor of the miscibility of polymer blends as noted under the IUPAC definition, it is very useful as an indicator of transitions in phase behavior and of the existence of compositions that are able to produce suitable blends for those specific applications, especially in film packaging.…”