Fractality and metastability of a complex amide cross-linked dipodal alkyl/siloxane hybrid

Abstract

A novel room-temperature white light emitter amide-cross linked alkyl/siloxane hybrid material (amidosil A) was produced by selforganization through the rational design of the precursor. This hybrid displays a highly complex hierarchical architecture composed of two lamellar bilayer structures, the relative spatial arrangement of which yields a multiplicity of ordered nanodomains with variable shapes and sizes, some of them persisting at the microscale. Macroscopically A was obtained as clusters of hydrophobic hemispherical 10 and spherical micro-objects exhibiting a lettuce coral-like pattern, which represent unprecedented pieces of evidence illustrating the principles of self-similarity and demonstrating that the time scale of biomimetic morphogenesis in this non-bridged silsesquioxane is similar to that in biological systems. Heating metastable A above the order/disorder phase transition acted as an external quake driving the material to another metastable state, which has persisted for more than 12 months, and was manifested as a marked change of all the macroscopic properties. The occurrence of the self-organization process operating on A, instead of a self-directed assembly, is primarily 15 associated with the formation/rupture of hydrogen bonds, therefore supporting that these interactions are critical factors dictating on what side of the self-assembly/self-organization boundary will a non-bridged silsesquioxane system evolve.

Structuring of Amide Cross‐Linked Non‐Bridged and Bridged Alkyl‐Based Silsesquioxanes

“…These unprecedented findings unequivocally demonstrated that we succeeded in producing a non‐bridged silsesquioxane material in which the time scale of the morphogenesis was such that it became possible to capture two different types of shapes and morphologies, associated with two distinct stages of the process: hemispheres, which represented an advanced phase of self‐similar branching (fractal growth), and closed spherocrystals, which corresponded to its completion …”

“…The design of the new precursor 4 included a secondary amide group and a tertiary amide group both linked to pendant alkyl chains with 13 carbon atoms (Figure ). This modification gave rise to two lamellar bilayer structures, which resulted in a series of unique nanoregions, some of which manifested at the microscale . Macroscopically the hybrid system was obtained as clusters of hydrophobic hemispherical and spherical micro‐objects exhibiting a lettuce coral‐like pattern (Figure A).…”

“…Equally interesting was the fact that heating this metastable hybrid above the order/disorder phase transition acted as an external quake, driving the material to another metastable state, which persisted for more than 12 months and led to a significant change of all the macroscopic properties (Figure B) …”

Novel Highly Luminescent Amine-Functionalized Bridged Silsesquioxanes

“…BSs incorporating hydrophobic alkyl chains and suitable cross-links composed of hydrogen donor and acceptor groups able to establish hydrogen bonding interactions (e.g., a urea or an amide groups) have been extensively explored (Moreau et al, 2001 ; Besson et al, 2010 ; Fernandes et al, 2011b ; Nunes et al, 2015b ). A convenient and widely used strategy to promote structuring in NBSs is the use of non-bridged organosilanes carrying exclusively pendant alkyl chains (Parikh et al, 1997 ; Shimojima et al, 1997 ) or alternatively alkyl chains and suitable cross-links (Carlos et al, 2007 ; Nunes et al, 2012 , 2013 , 2014a , b , 2015a ; Fernandes et al, 2013 ). A completely different approach was introduced by Besnard et al ( 2013 , 2016 ) to tune the structure of aminoundecyltriethoxysilane-derived silsesquioxanes in acidified water.…”

Structuring of Alkyl‐Triazole Bridged Silsesquioxanes

“…[1]. Materials from the natural world are known to be complex systems which provide plenty of inspiring examples of hierarchical arrangement, self‐similarity growth and emergent phenomena. In the last few years biomimetic strategies have been extensively adopted by the community of materials science with the goal of designing innovative materials exhibiting the extraordinary features offered by materials in Nature.…”