Liquid-crystalline polymers containing mesogenic units based on half-disk and rodlike moieties. 5. Side-chain liquid-crystalline poly(methylsiloxanes) containing hemiphasmidic mesogens based on 4-[[3,4,5,-tris(alkan-1-yloxy)benzoyl]oxy]-4'-[[p-(propan-1-yloxy)benzoyl]oxy]biphenyl groups

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.

Polysiloxane-Based Side Chain Liquid Crystal Polymers: From Synthesis to Structure⁻Phase Transition Behavior Relationships

Organosilicon polymer materials play an important role in certain applications due to characteristics of much lower glass transition temperatures (Tg), viscosities, surface energy, as well as good mechanical, thermal stabilities, and insulation performance stemming from the higher bond energy and the larger bond angles of the adjacent silicon-oxygen bond. This critical review highlights developments in the synthesis, structure, and phase transition behaviors of polysiloxane-based side chain liquid crystal polymers (PSCLCPs) of linear and cyclic polysiloxanes containing homopolymers and copolymers. Detailed synthetic strategies are elaborated, and the relationship between molecular structures and liquid crystalline phase transition behaviors is systematically discussed, providing theoretical guidance on the molecular design of the materials.

Thermoplastic High Strain Multishape Memory Polymer: Side-Chain Polynorbornene with Columnar Liquid Crystalline Phase

A thermoplastic high strain multishape memory polymer can be fabricated using a hemiphasmid side-chain polynorbornene (P1) with hexagonal columnar liquid crystalline (Φ_H ) phase. Without any chemical crosslinks, P1 can memorize multiple temporary shapes with high strain and exhibit excellent shape fixity and shape recovery. As the building blocks of Φ_H , the multichain columns in P1 act as robust physical crosslinks.

Self-organization behaviours of hemiphasmidic side-chain liquid-crystalline polymers with different spacer lengths

The influence of flexible spacers on unusual self-organization behaviours of side-chain liquid-crystalline polymers containing biphenyl hemiphasmidic mesogens.

Synthesis and self-organization of azobenzene containing hemiphasmidic side-chain liquid-crystalline polymers with different spacer lengths

Hemiphasmidic side-chain liquid-crystal polymers form different columnar phases depending on the spacer lengthnand temperatureT.

Poly(vinyl benzoate)-backbone mesogen-jacketed liquid crystalline polymers

This work describes a new system of MJLCPs with poly(vinyl benzoate)-backbone, which are efficiently synthesized by the bulk photo-polymerization method. Furthermore, homogeneous- or homeotropic-aligned cross-linked MJLCP (xMJLCP) films are for the first time successfully prepared.

Side chain liquid crystalline polymers with an optically active polynorbornene backbone and achiral mesogenic side groups

This work describes a series of side-on and end-on SCLCPs with an optically active polynorbornene main chain and achiral mesogens. The side-on SCLCPs tend to form achiral mesophases, while their comparative end-on analogues exhibit chiral mesophases.

Self-Organized Columnar Phase of Side-Chain Liquid Crystalline Polymers: To Precisely Control the Number of Chains Bundled in a Supramolecular Column

Self-organization of liquid crystalline (LC) polyacetylene derivatives (PAs) bearing hemiphasmid side-chains was investigated. The synthesized PAs can form smectic and columnar phases, depending on the constitutions of side chains. With a nanosegregation structure, the columnar phase of PAs takes a bundle of chains as its building block, of which the chain number is precisely determined by the volume fraction of the rigid component in PAs. The "precise multi-chain column" can be understood using a mean field theory, from which the deduced number of chains in the supramolecular column agrees well with the experimental result. This study reveals that the volume fraction of the rigid component plays a significant role in the self-organization of side-chain LC polymers, which is valuable for the rational design of macromolecules with precisely ordered structures.

Hemiphasmidic Side-Chain Liquid Crystalline Polymer: From Smectic C Phase to Columnar Phase with a Bundle of Chains as Its Building Block

We synthesized a new hemiphasmidic side-chain liquid crystalline polymer (P-n, n is the number of carbons in alky tail of the side chain, n = 4-12) using free radical polymerization. The side chain of P-n has a biphenyl in the middle, linked to the polystyrene backbone and to the terminal phenyl group with three alkyl tails via only methyleneoxy units. Upon increasing n, the mesophase of P-n changes from bilayer smectic C to hexagonal columnar (Φ_h) phase with the a-dimension of ∼6 nm. Both of the mesophases are long-range ordered, which can be well aligned by simple shearing. The oriented Φ_h shows a quite low rotational disorder around the shear direction. Most likely, the Φ_h phase takes a bundle of chains (e.g., ∼five chains) rather than a single chain as its building block. This "multi-chain model" of the Φ_h phase may represent a new type of self-assembly in side-chain polymers.

Self-Assembling Phenylpropyl Ether Dendronized Helical Polyphenylacetylenes

The first example of a self-assembling phenylpropyl ether based dendronized polymer has been reported and its preferred helical handedness has been determined. Dendronized polymer poly(10) and its nondendritic analogue poly(8) are high-cis-content polyphenylacetylenes (PPAs) prepared by using [Rh(nbd)Cl]2/NEt3 (nbd: 2,5-norbornadiene). Both polymers possess a stereocenter in their side chain, which selects a preferred helical handedness. Based on negative exciton chirality observed in the CD spectra of poly(10), we have designated this molecule as a right-handed helical polymer, which persists over a wide temperature range. Poly(10) self-organizes into both Phiioh and Phih lattices in bulk. The Phiioh-to-Phih transition is associated with thermoreversible cis-cisoidal to cis-transoidal isomerization of the helical PPA, accompanied by a dramatic decrease in the column diameter and a decrease in the pi-stacking correlation length along the column. A model for the right-handed helical dendronized PPA has been proposed wherein dendrons from adjacent column strata interdigitate to effectively fill space.

Bioinspired supramolecular liquid crystals

A brief account on the historical events leading to the discovery of self-assembling dendrons that generate self-organizable supramolecular dendrimers, or supramolecular polymers, and self-organizable dendronized polymers is provided. These building blocks were accessed by an accelerated design strategy that involves structural and retrostructural analysis of periodic and quasi-periodic assemblies. This design strategy mediated the discovery of porous helical supramolecular structures that self-assembled from dendritic dipeptides. Helical porous columns are the closest mimics of biologically related structures, such as tobacco mosaic virus coat, porous transmembrane proteins, porous pathogens and antibiotics. It is expected that this concept will allow one to investigate the structural origin of functions in synthetic supramolecular materials.

Poly(oxazoline)s with tapered minidendritic side groups as models for the design of synthetic macromolecules with tertiary structure. A demonstration of the limitations of living polymerization in the design of 3-D structures based on single polymer chains

The synthesis and living cationic ring-opening polymerization of 2-[3,4-bis(n-alkan-1-yloxy)phenyl]-2-oxazolines with alkan being tetradecan and pentadecan, i.e., (3,4)nG1-Oxz with n = 14 and 15, is described. The structural analysis of the resulting polymers with well-defined molecular weights and narrow molecular weight distribution was carried out by a combination of techniques, including differential scanning calorimetry (DSC), thermal optical polarized microscopy (TOPM), and X-ray diffraction (XRD). At low molecular weights both polymers self-assemble into spherical supramolecules that self-organize into a Pm3n 3-D lattice while at high molecular weights they form cylindrical macromolecules that self-organize into a p6mm 2-D hexagonal columnar lattice. Both polymers exhibit a 3-D shape change as a function of their degree of polymerization as was reported for the first time in a previous publication from our laboratory (Percec, V.; Ahn, C.-H; Ungar, G.; Yeardley, D. J. P.; Möller, M.; Sheiko, S. S. Nature (London) 1998, 391, 161). Since these polymers can be obtained via a living polymerization, a detailed mechanistic investigation of the influence of the degree of polymerization and molecular weight distribution on the formation of a 3-D spherical macromolecule from a single polymer chain, i.e., a tertiary structure, was possible. The experimental results have demonstrated that the synthesis of nonbiological macromolecules exhibiting tertiary structure is possible in at most a few percent of all macromolecules via living polymerization. This is the case even when macromolecules with very narrow molecular weight distributions and well-defined molecular weights are used. Therefore, the design of synthetic macromolecules with tertiary structure requires not only chains with well-defined molecular weight but also, in particular, macromolecules with no distribution of their chain length.

Poly(oxazolines)s with tapered minidendritic side groups. The simplest cylindrical models to investigate the formation of two-dimensional and three-dimensional order by direct visualization

The synthesis of 2-[3,4-bis(n-alkan-1-yloxy)phenyl]-2-oxazolines with alkan = octan, decan, dodecan, and tridecan is presented. Their living cationic ring opening polymerization produces cylindrical macromolecules that self-organize in a hexagonal columnar two-dimensional phase. The structural analysis of these polymers was carried out by a combination of techniques including differential scanning calorimetry, thermal optical polarized microscopy, X-ray diffraction, transmission electron microscopy, electron diffraction, scanning force microscopy, and atomic force microscopy (AFM). The diameter of these cylindrical macromolecules ranges from 33 to 44 A, and therefore they represent the simplest cylindrical macromolecules that can be directly visualized by AFM on a surface. Preliminary experiments have demonstrated the use of these cylindrical macromolecules as models to investigate the creation of two-dimensional and three-dimensional order via direct visualization and thus they represent the simplest nonbiological systems that mimic the role played by the complexes of nucleic acids with proteins in structural analysis by direct visualization.

Cell membrane as a model for the design of ion-active nanostructured supramolecular systems

The synthesis and polymerization of six AB(3) tapered self-assembling methacrylate monomers (5a, 5b, 5c,5d, 17a, and 17b) based on first generation alkyl substituted benzyl ether monodendrons (i.e., minidendrons) containing oligooxyethylene units at their focal point and the polymerizable group on their periphery are described. The corresponding polymers (6a, 6b, 6c, 6d, 18a, and 18b) self-assemble and subsequently self-organize in supramolecular networks that form a 2-D hexagonal lattice. This network consists of a continuous phase based on a paraffin barrier material perforated in a hexagonal array by ion-active channels constructed from the oligooxyethylenic units protected by the aromatic groups of the taper. Complexation of the oligooxyethylene channels of 6a-d with LiCF(3)SO(3) salt enhances the thermal stability of their hexagonal columnar (phi(h)) liquid crystalline phase. The enhancement of the thermal stability of the phi(h) phase of both monomers and polymers up to 86 degrees C is also achieved by shifting the placement of the polymerizable group from the 3 position to the 4 position of the 3,4,5-trisubstituted AB(3) benzoate monodendrons. The design of these macromolecules was inspired by the bilayer fluid mosaic structure of the cell membrane. The lipid bilayer of the cell membrane that acts in its ordered state as a barrier to the passage of polar molecules was replaced with the paraffinic barrier, while the protein-based ionic channels were replaced with oligooxyethylenic-based channels. The resulted supramolecular material has the mechanical integrity required for the design of ion-active nanostructured supramolecular systems.