Abstract
Dendronized polyethers give rise to columnar LC structures which can successfully act as cation transport materials. Therefore, we prepared two different materials, based on Poly(epichlorohydrin-co-ethylene oxide) (PECH-co-EO) grafted with methyl 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy] benzoate, containing 20% or 40% modified units, respectively. The obtained polymers were characterized by differential scanning calorimetry (DSC), X-ray diffraction and optical microscopy between crossed polars (POM) and compared to the unmodified PECH-co-EO. In order to reach efficient transport properties, homeotropically oriented membranes were prepared by a fine-tuned thermal annealing treatment and were subsequently investigated by dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA). We found that the presence of the dendrons induces a main chain partial crystallization of the polyether chain and coherently increases the polymer Tg. This effect is more evident in the oriented membranes. As for copolymer orientation upon annealing, the cooling rate and the annealing temperature were the most crucial factors. DMTA and DETA confirmed that grafting with the dendron strongly hinders copolymer motions, but did not show great differences between unoriented and oriented membranes, regardless of the amount of dendrons.
Highlights
Percec and co-workers were the first to discover and examine the intramolecular self-assembly and self-organization processes of side-chain liquid-crystalline polymers (SCLCPs) into columnar structures, in which the main polymer chain is arranged into a helical inner channel surrounded by the side-chain dendrons due to an exo-recognition process of the aromatic moieties in the side-chain mesogenic groups [17,18]
The synthesis of side-chain liquid-crystalline polyethers and polyamines bearing different amounts of the dendron 3,4,5-tris[4-(n-dodecan-1-yloxy)bezyloxy]benzoate (Tap) grafted to the polymer backbone that self-assemble into a columnar structure and the subsequent preparation of membranes derived from these SCLCPs have been extensively studied by our research group [19,20,21,22]
It was shown that no improvement resulted from either changing the solvent to NMP or DMF, or increasing the Tap/chlorine molar ratio above 1:1 [19]
Summary
Since Daniel Vorländer described in 1923 the synthesis of the first polymers that contains benzenes connected by ester bonds in the main chain [1], LCP (liquid-crystalline polymers) have been widely investigated due to their exceptional mechanical, optical and electrical properties [2,3], with their unique attribute being that LC phases can flow like liquids and can preserve the natural anisotropic structure of the glassy solid state [4,5].This singular combination of properties is responsible for the wide range of applications that LCP presents, such as in optical data storage [6], non-linear optics [7], optical compensators [8], electronic devices [9], solid polymer electrolytes [10] and separation membranes [11]. Since Daniel Vorländer described in 1923 the synthesis of the first polymers that contains benzenes connected by ester bonds in the main chain [1], LCP (liquid-crystalline polymers) have been widely investigated due to their exceptional mechanical, optical and electrical properties [2,3], with their unique attribute being that LC phases can flow like liquids and can preserve the natural anisotropic structure of the glassy solid state [4,5]. The presence of electronegative atoms like oxygen or nitrogen in the polymeric backbone could favour interaction with cations, providing hydrophobic selective transport systems that exhibit proton permeability compared to
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