Oligodimethylsiloxane-Oligoproline Block Co-Oligomers: the Interplay between Aggregation and Phase Segregation in Bulk and Solution

Abstract

Discrete block co-oligomers (BCOs) assemble into highly ordered nanostructures, which adopt a variety of morphologies depending on their environment. Here, we present a series of discrete oligodimethylsiloxane-oligoproline ( o DMS- o Pro) BCOs with varying oligomer lengths and proline end-groups, and study the nanostructures formed in both bulk and solution. The conjugation of oligoprolines to apolar siloxanes permits a study of the aggregation behavior of oligoproline moieties in a variety of solvents, including a highly apolar solvent like methylcyclohexane. The apolar solvent is more reminiscent of the polarity of the siloxane bulk, which gives insights into the supramolecular interactions that govern both bulk and solution assembly processes of the oligoproline. This extensive structural characterization allows the bridging of the gap between solution and bulk assembly. The interplay between the aggregation of the oligoproline block and the phase segregation induced by the siloxane drives the assembly. This gives rise to disordered, micellar microstructures in apolar solution and crystallization-driven lamellar nanostructures in the bulk. While most di- and triblock co-oligomers adopt predictable morphological features, one of them, o DMS 15 - o Pro 6 -NH 2 , exhibits pathway complexity leading to gel formation. The pathway selection in the complex interplay between aggregation and phase segregation gives rise to interesting material properties.

Determination of the critical chain length for macromolecular crystallization using structurally flexible polyketones

“…Interestingly, the recent developments such as the iterative exponential growth (IEG) strategy facilitate an efficient synthetic access to discrete oligomers. 9,10 Over the last few decades, a wide variety of discrete oligomers including oligo((meth)acrylate)s, 11,12 oligo(ethylene imine)s, [13][14][15] oligo(caprolactone)s, [16][17][18] oligo(siloxane)s, [19][20][21][22] oligo(thiophene)s, [23][24][25] and oligo(peptide)s [26][27][28][29] have been investigated. These oligomers aid in discovering length-specific properties, for example, aggregation, folding, host-guest interactions, and light absorption, that are otherwise hidden in polydisperse polymers.…”

Building-block approach to discrete and sequence-specific oligosiloxanes

“…For example, Meijer et al achieved the synthesis of oligodimethylsiloxanes up to 40-mer on a multigram scale using IEG. [17][18][19][20] However, IEG has limitations in terms of precisely controlling both the degree of polymerization and sequence structure. Therefore, to synthesize discrete and sequencespecific oligomers with the desired control over both the degrees of polymerization and sequence structure, linear monodirectional iterations would be an ideal choice.…”

Supramolecular polymers: Recent advances based on the types of underlying interactions

“…[67][68][69][70][71][72][73][74] The emergence of UPy-based polymers marked the beginning of the rapid development of supramolecular polymeric materials. Since then, research on supramolecular polymers blossomed, with key advances coming not only from Meijer, [21][22][23][74][75][76][77] but also Leibler, [41,78] Zimmerman, [79,80] Craig, [81][82][83] Bouteiller, [84][85][86] Binder, [87,88] Zhang, [89][90][91] Gibson, [92][93][94] Long, [95,96] and others. [97] Several of the authors of this review have also contributed to the development of the field.…”