Dramatic Stabilization of a Hexagonal Columnar Mesophase Generated from Supramolecular and Macromolecular Columns by the Semifluorination of the Alkyl Groups of Their Tapered Building Blocks

From Frank-Kasper, Quasicrystals, and Biological Membrane Mimics to Reprogramming In Vivo the Living Factory to Target the Delivery of mRNA with One-Component Amphiphilic Janus Dendrimers

This Perspective is dedicated to the 25th Anniversary of Biomacromolecules. It provides a personal view on the developing field of the polymer and biology interface over the 25 years since the journal was launched by the American Chemical Society (ACS). This Perspective is meant to bridge an article published in the first issue of the journal and recent bioinspired developments in the laboratory of the corresponding author. The discovery of supramolecular spherical helices self-organizing into Frank-Kasper and quasicrystals as models of icosahedral viruses, as well as of columnar helical assemblies that mimic rodlike viruses by supramolecular dendrimers, is briefly presented. The transplant of these assemblies from supramolecular dendrimers to block copolymers, giant surfactants, and other self-organized soft matter follows. Amphiphilic self-assembling Janus dendrimers and glycodendrimers as mimics of biological membranes and their glycans are discussed. New concepts derived from them that evolved in the in vivo targeted delivery of mRNA with the simplest one-component synthetic vector systems are introduced. Some synthetic methodologies employed during the synthesis and self-assembly are explained. Unraveling bioinspired applications of novel materials concludes this brief 25th Anniversary Perspective of Biomacromolecules.

Screening Libraries to Discover Molecular Design Principles for the Targeted Delivery of mRNA with One-Component Ionizable Amphiphilic Janus Dendrimers Derived from Plant Phenolic Acids

Viral and synthetic vectors to deliver nucleic acids were key to the rapid development of extraordinarily efficient COVID-19 vaccines. The four-component lipid nanoparticles (LNPs), containing phospholipids, PEG-conjugated lipids, cholesterol, and ionizable lipids, co-assembled with mRNA via a microfluidic technology, are the leading nonviral delivery vector used by BioNTech/Pfizer and Moderna to access COVID-19 mRNA vaccines. LNPs exhibit a statistical distribution of their four components when delivering mRNA. Here, we report a methodology that involves screening libraries to discover the molecular design principles required to realize organ-targeted mRNA delivery and mediate activity with a one-component ionizable multifunctional amphiphilic Janus dendrimer (IAJD) derived from plant phenolic acids. IAJDs co-assemble with mRNA into monodisperse dendrimersome nanoparticles (DNPs) with predictable dimensions, via the simple injection of their ethanol solution in a buffer. The precise location of the functional groups in one-component IAJDs demonstrated that the targeted organs, including the liver, spleen, lymph nodes, and lung, are selected based on the hydrophilic region, while activity is associated with the hydrophobic domain of IAJDs. These principles, and a mechanistic hypothesis to explain activity, simplify the synthesis of IAJDs, the assembly of DNPs, handling, and storage of vaccines, and reduce price, despite employing renewable plant starting materials. Using simple molecular design principles will lead to increased accessibility to a large diversity of mRNA-based vaccines and nanotherapeutics.

Stimuli-Responsive Principles of Supramolecular Organizations Emerging from Self-Assembling and Self-Organizable Dendrons, Dendrimers, and Dendronized Polymers

All activities of our daily life, of the nature surrounding us and of the entire society and its complex economic and political systems are affected by stimuli. Therefore, understanding stimuli-responsive principles in nature, biology, society, and in complex synthetic systems is fundamental to natural and life sciences. This invited Perspective attempts to organize, to the best of our knowledge, for the first time the stimuli-responsive principles of supramolecular organizations emerging from self-assembling and self-organizable dendrons, dendrimers, and dendronized polymers. Definitions of stimulus and stimuli from different fields of science are first discussed. Subsequently, we decided that supramolecular organizations of self-assembling and self-organizable dendrons, dendrimers, and dendronized polymers may fit best in the definition of stimuli from biology. After a brief historical introduction to the discovery and development of conventional and self-assembling and self-organizable dendrons, dendrimers, and dendronized polymers, a classification of stimuli-responsible principles as internal- and external-stimuli was made. Due to the enormous amount of literature on conventional dendrons, dendrimers, and dendronized polymers as well as on their self-assembling and self-organizable systems we decided to discuss stimuli-responsive principles only with examples from our laboratory. We apologize to all contributors to dendrimers and to the readers of this Perspective for this space-limited decision. Even after this decision, restrictions to a limited number of examples were required. In spite of this, we expect that this Perspective will provide a new way of thinking about stimuli in all fields of self-organized complex soft matter.

An Accelerated Modular-Orthogonal Ni-Catalyzed Methodology to Symmetric and Nonsymmetric Constitutional Isomeric AB2 to AB9 Dendrons Exhibiting Unprecedented Self-Organizing Principles

Five libraries of natural and synthetic phenolic acids containing five AB₃, ten constitutional isomeric AB₂, one AB₄, and one AB₅ were previously synthesized and reported by our laboratory in 5 to 11 steps. They were employed to construct seven libraries of self-assembling dendrons, by divergent generational, deconstruction, and combined approaches, enabling the discovery of a diversity of supramolecular assemblies including Frank-Kasper phases, soft quasicrystals, and complex helical organizations, some undergoing deracemization in the crystal state. However, higher substitution patterns within a single dendron were not accessible. Here we report three libraries consisting of 30 symmetric and nonsymmetric constitutional isomeric phenolic acids with unprecedented sequenced patterns, including two AB₂, three AB₃, eight AB₄, five AB₅, six AB₆, three AB₇, two AB₈, and one AB₉ synthesized by accelerated modular-orthogonal Ni-catalyzed borylation and cross-coupling. A single etherification step with 4-(n-dodecyloxy)benzyl chloride transformed all these phenolic acids, of interest also for other applications, into self-assembling dendrons. Despite this synthetic simplicity, they led to a diversity of unprecedented self-organizing principles: lamellar structures of interest for biological membrane mimics, helical columnar assemblies from rigid-solid angle dendrons forming Tobacco Mosaic Virus-like assemblies, columnar organizations from adaptable-solid angle dendrons forming disordered micellar-like nonhelical columns, columns from supramolecular spheres, five body-centered cubic phases displaying supramolecular orientational memory, rarely encountered in previous libraries forming predominantly Frank-Kasper phases, and two Frank-Kasper phases. Lessons from these self-organizing principles, discovered within a single generation of self-assembling dendrons, may help elaborate design principles for complex helical and nonhelical organizations of synthetic and biological matter.

Hydrogen-bonded mesomorphic complexes combining hydrophilic and fluorophilic molecular segments

A 2,4-diamino-6-phenyl-1,3,5-triazine carrying a single oligo(ethylene oxide) (EO) chain has been investigated in binary mixtures with two-chain and three-chain semiperfluorinated benzoic acids. Mixtures of the triazine with three equivalents of the complementary acids exhibit a hexagonal columnar (Col_h) mesophase. Docking of three acid molecules to the diaminotriazine nucleus leads to the formation of disc-like aggregates with a central hydrogen-bonded polar core surrounded by the peripheral fluoroalkyl chains, which self-assemble in columns arranged on a hexagonal lattice. The polar EO chains at the triazine cores do not segregate into a distinct sub-space but are included into the polar cores, providing increased flexibility of the cores with respect to conformations and available hydrogen bonding sites. In equimolar (1 : 1) triazine/benzoic acid mixtures macroscopic phase separation of excess triazine from the columnar LC phases occurs. These Col_h phases are formed by [1 : 3] or [2 : 4] complexes, depending on the number of fluorinated chains. However, some of the excess triazine component is accommodated within the polar column cores, contributing to space filling and providing additional hydrogen bonding along the columns. Thus the EO chain, despite of being fixed at the periphery, assemble in the core region of the aggregates, this is distinct from the self-assembly of related alkyl or semiperfluoroalkyl substituted diaminotriazines with fluorinated benzoic acids, forming discrete disc-like [1 : 3] or rod-like [1 : 1] complexes. Obviously, the flexible EO chains decrease the effect of the aggregate shape on self-assembly and lead to an increased contribution of general amphiphilicity to self-assembly.

SET-LRP in biphasic mixtures of fluorinated alcohols with water

Efficient and inexpensive SET-LRP in biphasic-mixtures of fluorinated alcohols with water.

Polyphilic hydrogen bonded block molecules involving semiperfluorinated and silylated molecular fragments

2,4-Diamino-6-phenyl-1,3,5-triazines grafted with one or two semiperfluorinated chains at the phenyl substituent have been investigated in binary mixtures with one-chain and two-chain oligo(dimethylsiloxy) terminated 4-alkoxy- and 3,4-dialkoxybenzoic acids. Equimolar mixtures of the triazines with the complementary acids form discrete double hydrogen-bonded heterodimers with an elongated central core. Mesomorphic properties are observed only if at least two terminal fluoroalkyl chains are attached to the triazine entity. Three to four heterodimers generate aggregates with preferably parallel adjusted rod-like H-bonded cores. The space requirement of the segregated peripheral fluoroalkyl and oligosiloxane segments considerably exceeds that of the central core region, leading to an overall circular geometry of the associates which organize in columnar LC phases. The chains initiate a local segregation which is however not long range and retains a time and space averaged two-dimensional hexagonal lattice.

Searching for efficient SET-LRP systems via biphasic mixtures of water with carbonates, ethers and dipolar aprotic solvents

Screening biphasic mixtures of water with carbonates, ethers and dipolar aprotic solvents to discover new SET-LRP solvent systems.

Screening Libraries of Semifluorinated Arylene Bisimides to Discover and Predict Thermodynamically Controlled Helical Crystallization

Synthesis, structural, and retrostructural analysis of a library containing 16 self-assembling perylene (PBI), 1,6,7,12-tetrachloroperylene (Cl₄PBI), naphthalene (NBI), and pyromellitic (PMBI) bisimides functionalized with environmentally friendly AB₃ chiral racemic semifluorinated minidendrons at their imide groups via m = 0, 1, 2, and 3 methylene units is reported. These semifluorinated compounds melt at lower temperatures than homologous hydrogenated compounds, permitting screening of all their thermotropic phases via structural analysis to discover thermodynamically controlled helical crystallization from propeller-like, cogwheel, and tilted molecules as well as lamellar-like structures. Thermodynamically controlled helical crystallization was discovered for propeller-like PBI, Cl₄PBI and NBI with m = 0. Unexpectedly, assemblies of twisted Cl₄PBIs exhibit higher order than those of planar PBIs. PBI with m = 1, 2, and 3 form a thermodynamically controlled columnar hexagonal 2D lattice of tilted helical columns with intracolumnar order. PBI and Cl₄PBI with m = 1 crystallize via a recently discovered helical cogwheel mechanism, while NBI and PMBI with m = 1 form tilted helical columns. PBI, NBI and PMBI with m = 2 generate lamellar-like structures. 3D and 2D assemblies of PBI with m = 1, 2, and 3, NBI with m = 1 and PMBI with m = 2 exhibit 3.4 Å π-π stacking. The library approach applied here and in previous work enabled the discovery of six assemblies which self-organize via thermodynamic control into 3D and 2D periodic arrays, and provides molecular principles to predict the supramolecular structure of electronically active components.

Self-Sorting and Coassembly of Fluorinated, Hydrogenated, and Hybrid Janus Dendrimers into Dendrimersomes

The modular synthesis of a library containing seven self-assembling amphiphilic Janus dendrimers is reported. Three of these molecules contain environmentally friendly chiral-racemic fluorinated dendrons in their hydrophobic part (RF), one contains achiral hydrogenated dendrons (RH), while one denoted hybrid Janus dendrimer, contains a combination of chiral-racemic fluorinated and achiral hydrogenated dendrons (RHF) in its hydrophobic part. Two Janus dendrimers contain either chiral-racemic fluorinated dendrons and a green fluorescent dye conjugated to its hydrophilic part (RF-NBD) or achiral hydrogenated and a red fluorescent dye in its hydrophilic part (RH-RhB). These RF, RH, and RHF Janus dendrimers self-assembled into unilamellar or onion-like soft vesicular dendrimersomes (DSs), with similar thicknesses to biological membranes by simple injection from ethanol solution into water or buffer. Since RF and RH dendrons are not miscible, RF-NBD and RH-RhB were employed to investigate by fluorescence microscopy the self-sorting and coassembly of RF and RH as well as of phospholipids into hybrid DSs mediated by the hybrid hydrogenated-fluorinated RHF Janus dendrimer. The hybrid RHF Janus dendrimer coassembled with both RF and RH. Three-component hybrid DSs containing RH, RF, and RHF were formed when the proportion of RHF was higher than 40%. With low concentration of RHF and in its absence, RH and RF self-sorted into individual RH or RF DSs. Phospholipids were also coassembled with hybrid RHF Janus dendrimers. The simple synthesis and self-assembly of DSs and hybrid DSs, their similar thickness with biological membranes and their imaging by fluorescence and (19)F-MRI make them important tools for synthetic biology.

Ionic Liquid Crystals: Versatile Materials

This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.

Influence of main-chain and molecular weight on the phase behaviors of side-chain liquid crystalline polymers without the spacer

The main-chain and molecular weight affects the clearing temperature of side-chain liquid crystalline polymers based on biphenyl mesogen without the spacer.

From structure to function via complex supramolecular dendrimer systems

Self-assembly of quasi-equivalent amphiphilic dendrons into secondary and tertiary structures and their self-organization into periodic arrays.

SET-LRP of semifluorinated acrylates and methacrylates

For the first time SET-LRP of 1H,1H,2H,2H-perfluorooctyl acrylate, 2,2,3,3,4,4,4-heptafluorobutyl acrylate, 1H,1H,5H-octafluoropentyl acrylate and 1H,1H,5H-octafluoropentyl methacrylate in 2,2,2-trifluoroethanol as the solvent at 25 °C for acrylates and at 50 °C for methacrylate was accomplished.