Periodically Clickable Polyesters: Study of Intrachain Self-Segregation Induced Folding, Crystallization, and Mesophase Formation

Abstract

A series of polyesters based on 2-propargyl-1,3-propanediol or 2,2-dipropargyl-1,3-propanediol or 2-allyl-2-propargyl-1,3-propanediol and 1,20-eicosanedioic acid were prepared by solution polycondensation using the corresponding diacid chloride; these polyesters were quantitatively "clicked" with a fluoroalkyl azide, namely CF3(CF2)7CH2CH2N3, to yield polyesters carrying long-chain alkylene segments in the backbone and either one or two perfluoroalkyl segments located at periodic intervals along the polymer chain. The immiscibility of the alkylene and fluoroalkyl segments causes the polymer chains to fold in a zigzag fashion to facilitate the segregation of these segments; the folded chains further organize in the solid state to form a lamellar structure with alternating domains of alkyl (HC) and fluoroalkyl (FC) segments. Evidence for the self-segregation is provided by DSC, SAXS, WAXS, and TEM studies; in two of the samples, the DSC thermograms showed two distinct endotherms associated with the melting of the individual domains, while the WAXS patterns confirm the existence of two separate peaks corresponding to the interchain distances within the crystalline lattices of the HC and FC domains. SAXS data, on the other hand, reveal the formation of an extended lamellar morphology with an interlamellar spacing that matches reasonably well with those estimated from TEM studies. Interestingly, a smectic-type liquid crystalline phase is observed at temperatures between the two melting transitions. These systems present a unique opportunity to develop interesting nanostructured polymeric materials with precise control over both the domain size and morphology; importantly, the domain sizes are far smaller than those typically observed in traditional block copolymers.

Synthesis of Non-Natural Sequence-Encoded Polymers Using Phosphoramidite Chemistry

“…50 The synthesis of d-1' was adapted from the literature. 55 D-0 and 0 were synthesized according to reported procedures. 56 All air-sensitive reactions have been carried out under argon atmosphere.…”

Criss‐cross amphiphilic polymers and analogous model systems

“…They also demonstrated the profound effect of periodicity of the substituent on the folding behavior and the lamellar dimensions; in case of randomly distributed branch points, the polymers were found to exhibit curved and segmented morphologies . More recently, our group has studied periodically grafted amphiphilic copolymers (PGACs) wherein, the immiscibility between the backbone and the pendant segments drives the polyethylene‐like backbone to fold in a zig–zag conformation excluding the pendant units; these folded structures were further stabilized by the crystallization of either backbone or both backbone and pendant segments . Remarkably, all these graft copolymers exhibit lamellar morphology with sub‐10 nm interlamellar spacing; here, the domain spacing can be controlled by either the periodicity of branching or by varying the size of the pendant segments …”

Thermally Crosslinkable and Chemically Modifiable Aromatic Polyesters Possessing Pendant Propargyloxy Groups

“…The combination of step‐growth polymerization and click chemistry modification has been put to use for synthesis of a range of graft copolymers and functionalized polymers . Click chemistry modifications of aliphatic polyesters containing pendant clickable groups such as alkyne, azide, alkene, and so on have been widely explored . Until now, to the best of our knowledge, limited information is available on click chemistry modification of aromatic polyesters with a notable exception of polyesters with pendant azido groups or alkene groups …”