Discrete Giant Polymeric Chains Based on Nanosized Monomers

Abstract

As size-amplified analogues of canonical macromolecules, polymeric chains built up by “giant” monomers represent an experimental realization of the “beads-on-a-string” model at larger length scales, which could provide insights into fundamental principles of polymer science. In this work, we modularly constructed discrete giant polymeric chains using nanosized building blocks (polyhedral oligomeric silsesquioxane, POSS) as basic repeat units through an efficient and robust iterative exponential growth approach, with precise control on molecular parameters, including size, composition, regioconfiguration, and surface functionalities. Their chemical structures were fully characterized by nuclear magnetic resonance spectroscopy, size-exclusion chromatography, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. With elaborately designed amphiphilic block POSS chains and their analogues made of conventional monomers, the size effects were delicately studied and highlighted. Interesting assembly behaviors emerge as a result of distinct interactions and molecular dynamics. This category of molecules shares general self-assembly characteristics as the conventional counterparts in terms of phase transition and evolution. Meanwhile, it turns out that the monomer size has profound impacts on phase stability, as a trade-off between entropic and enthalpic contributions. It may open up a door for modular and programmable design of interesting materials with complex structures and diverse functions.

Precise Amphiphilic Giant Polymeric Chain Based on Nanosized Monomers with Exact Regio-Configuration

“…With these isomeric CPOSS monomers, discrete CPOSS chains with precisely defined regio-configuration ( para -, meta -, and ortho -CPOSS n , labeled as p -, m -, o -C n ; Scheme b) were modularly prepared (Schemes S3 and S4; Figure S6). Like the monomer, 1 H NMR and MALDI-ToF MS for all three isomeric homochains are essentially identical since they have the same chemical compositions (Figures S7 and S8). Nevertheless, the distinct regio-regularity shows a profound influence on chain conformation, as revealed by clear and consistent shifts in SEC traces among these isomers (Figure S9).…”

“…Utilizing isomeric POSS monomers, discrete giant polymeric chains with corresponding regioregularity can be modularly prepared via the iterative exponential growth approach as reported in our earlier study (Scheme ). , By selectively installing two substituents at specific vertexes, the cubic symmetry of the T 8 -POSS cage ( O h ) can be reduced to C 2 v ( ortho - and meta -) and D 3 d ( para -) (Scheme S1, Figures S1 and S2). , In this study, a pair of mutually orthogonal functional groups, i .…”

“…Collective hydrogen bonding among the DPOSS cages provides a strong driving force for phase separation. It has been demonstrated that the giant POSS chains with para- configuration could self-assemble into diverse nanostructures, following general self-assembly characteristics as the conventional block copolymers . On the other hand, other factors such as molecular weight distribution, − conformational asymmetry, sequence, , and topo-/regio-configuration also have a profound impact on the formation and evolution of ordered structures.…”

“…As size-amplified analogues of canonical polymers at larger length scales, polymeric chains made of “giant” monomers allow direct observation of structural characteristics using optical microscopy or even the naked eye, offering an intriguing alternative for exploration of chain dynamics and phase behaviors. , Giant monomers usually refer to granular or colloidal particles with diameters ranging from millimeters to nanometers, such as Teflon beads, , water droplets, colloidal particles, − peptide bundles, globular proteins, or molecular clusters. − Through elaborately designed supramolecular recognition and/or chemical coupling, the giant monomers can be “polymerized” into particle arrays with a chain-like configuration. Compared with individual monomers, the connection along the main chain endows these giant polymeric chains with appealing properties through cumulative and collective effects .…”

“…As a result, inevitable defects severely impede the systematic studies and further applications. To circumvent these problems, we recently demonstrated a robust and efficient iterative exponential growth (IEG) approach to prepare discrete giant polymeric chains with uniform length using polyhedral oligomeric silsesquioxane (POSS, a precisely defined rigid nanoparticle with a diameter of 1–3 nm) as repeat units, providing an ideal model system to unravel the fundamental principles at a larger length scale …”