Polymorphism in the Assembly of Phase-Segregated Block Molecules: Pathway Control to 1D and 2D Nanostructures

Hawker

et al. 2021

Self Cite

Precise oligomeric materials constitute a growing area of research with implications for various applications as well as fundamental studies. Notably, this field of science which can be termed macro‐organic chemistry, draws inspiration from both traditional polymer chemistry and organic synthesis, combining the molecular precision of organic chemistry with the materials properties of macromolecules. Discrete oligomers enable access to unprecedented materials properties, for example, in self‐assembled structures, crystallization, or optical properties. The degree of control over oligomer structures resembles many biological systems and enables the design of materials with tailored properties and the development of fundamental structure–property relationships. This Review highlights recent developments in macro‐organic chemistry from synthetic concepts to materials properties, with a focus on self‐assembly and molecular recognition. Finally, an outlook for future research directions is provided.

Section: Self-assembly Driven By (Liquid) Crystallinitymentioning

confidence: 99%

Properties and applications of precision oligomer materials; where organic and polymer chemistry join forces

Genabeek

Hawker

et al. 2021

Self Cite

“…For the synthesis of oDMS conjugates, we used in many recent publications alkene-terminated oligomers or small molecules as substrates to couple to the discrete oDMS using Karstedt's catalyst (Figure 4A). 25,26,[31][32][33][34][35] Here, we discuss the general observations and byproduct formation during the Karstedt catalyzed hydrosilylation reaction.…”

Section: Synthesis Of Mono-and Bifunctional Discrete Odmsmentioning

confidence: 99%

The iterative synthesis of discrete dimethylsiloxane oligomers: A practical guide

Waal

Meijer

2020

Self Cite

Discrete dimethylsiloxane oligomers are interesting building blocks for the synthesis of high χ–low N block co‐oligomers (BCOs) forming highly organized nanostructures. Here, a practical guide to the synthesis of molecularly defined oligodimethylsiloxanes (oDMS) from 7‐mer to 40‐mer via a linear growth strategy is described. The iteration of a hydroxylation reaction and the condensation of mono‐ or bifunctional hydroxysiloxanes with chloro‐octamethyltetrasiloxane results in asymmetric and symmetric siloxanes, respectively. The synthesis contains critical washing and purification steps to remove minor amounts of low and high‐molecular weight byproducts, which are detected using Fourier transform infrared spectrometry, gas chromatography–mass spectrometry, and size‐exclusion chromatography. The oligomers are obtained on a multigram scale in yields of 94–50% and in high purity with only one molar mass detected. The formation of the chloride, hydroxide or hydride functional groups is adequately analyzed using 29Si NMR spectroscopy. The hydride terminated siloxane oligomers are used in Karstedt catalyzed hydrosilylation reactions with alkene‐functional substrates to obtain oDMS‐based oligomers and BCOs. Byproduct formation as a result of isomerization and reduction are followed by 1H NMR spectroscopy and minimized using dry conditions and low‐catalyst loadings.

“…38,39 Block co-oligomers with one block consisting of oligodimethylsiloxane (oDMS) of discrete length have been shown to assemble into well-defined phasesegregated structures with sub-10 nm feature sizes, due to the large Flory−Huggins interaction parameter (χ) and low degrees of polymerization (N) of these systems. 40 The introduction of azobenzene moieties in the rigid block has led to structures for sub-5 nm photopatterning, 41 with fast thermal transitions 42 triggered by the high degree of organization of the azobenzene units in spatially ordered domains. Hence, we envision that alternating copolymers combining azobenzene motifs and discrete oDMS blocks will allow the marriage of flexibility and nanoscale properties in polymeric materials.…”

Section: Introductionmentioning

confidence: 99%

Photo‐controlled alignment and helical organization in main‐chain liquid crystalline alternating polymers

Sakaino

Meskers

et al. 2021

Self Cite

Materials with highly ordered nanoscale structures can translate molecular processes to macroscopic function. Here we report on the photo‐controlled organization of achiral alternating copolymers composed of discrete length blocks showing well‐defined sub‐10 nm morphologies. These alternating copolymers consist of main‐chain azobenzene building blocks alternating with discrete oDMS blocks of various precise lengths. Remarkably, we demonstrate the imprinting of a stable helical molecular arrangement in spin‐casted thin films by irradiation with circularly polarized light, without chiral dopant or plasticizer required. By following the out‐of‐equilibrium photo‐switching process over irradiation time, the mechanism of molecular reorganization is unraveled and rationalized with the nature of the morphology. Linear photo‐organization is preferentially reached with flexible and symmetric cylindrical structures while helical photo‐organization is most easily obtained with robust but rotatable lamella structures. These findings suggest that precision in the synthesis and assembly of alternating copolymers can lead to complete control over molecular organization and main‐chain motion.