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The rapid decline in DNA sequencing costs has fueled the demand for nucleic acid collection to unravel genomic information, develop treatments for genetic diseases, and track emerging biological threats. Current approaches to maintaining these nucleic acid collections hinge on continuous electricity for maintaining low-temperature and intricate cold-chain logistics. Inspired by the millennia-long preservation of fossilized biological specimens in calcified minerals or glassy amber, we present Thermoset-REinforced Xeropreservation (T-REX): a method for storing DNA in deconstructable glassy polymer networks. Key to T-REX is the development of polyplexes for nucleic acid encapsulation, streamlining the transfer of DNA from aqueous to organic phases, replete with initiators, monomers, cross-linkers, and thionolactone-based cleavable comonomers required to form the polymer networks. This process successfully encapsulates DNA that spans different length scales, from tens of bases to gigabases, in a matter of hours compared to days with traditional silica-based encapsulation. Further, T-REX permits the extraction of DNA using comparatively benign reagents, unlike the hazardous hydrofluoric acid required for recovery from silica. T-REX provides a path toward low-cost, time-efficient, and long-term nucleic acid preservation for synthetic biology, genomics, and digital information storage, potentially overcoming traditional low-temperature storage challenges.

Polymer-protein bioconjugation offers a powerful strategy to alter the physical properties of proteins, and various synthetic polymer compositions and architectures have been investigated for this purpose. Nevertheless, conjugation of molecular bottlebrush polymers (BPs) to proteins remains an unsolved challenge due to the large size of BPs and a general lack of methods to transform the chain ends of BPs into functional groups suitable for bioconjugation. Here, we present a strategy to address this challenge in the context of BPs prepared by "graft-through" ring-opening metathesis polymerization (ROMP), one of the most powerful methods for BP synthesis. Quenching ROMP of PEGylated norbornene macromonomers with an activated enyne terminator facilitates the transformation of the BP Ru alkylidene chain ends into Pd oxidative addition complexes (OACs) for facile bioconjugation. This strategy is shown to be effective for the synthesis of two BP-protein conjugates (albumin and ERG), setting the stage for a new class of BP-protein conjugates for future therapeutic and imaging applications.

The concentrations of reactive oxygen species (ROS), e.g., H 2 O 2 , are often elevated in diseased tissue microenvironments. Therefore, the selective detection of ROS could enable new diagnostic methods or tools for chemical biology. Here, we report the synthesis of boronic ester-bis-norbornene core-cross-linked brush-arm star polymers (BASPs) with polyethylene glycol (PEG) or PEG- branch -spirocyclohexyl nitroxide (chex) shells. Size exclusion chromatography (SEC) and dynamic light scattering (DLS) showed that these BASPs have narrowly dispersed molar masses and average hydrodynamic diameters of 23 ± 2 nm, respectively. Moreover, due to their core-shell structures, these BASPs disassemble into bottlebrush fragments with improved selectivity for H 2 O 2 over ROS such as peroxynitrite (ONOO - ) and hypochlorite ( - OCl). Finally, H 2 O 2 induced disassembly of chex-containing BASPs induces a change in transverse magnetic relaxivity that can be detected via magnetic resonance imaging (MRI). Chex-BASPs may represent a valuable new diagnostic tool for H 2 O 2 sensing.

Polymer conjugation has been widely used to improve the stability and pharmacokinetics of therapeutic biomacromolecules; however, conventional methods to generate such conjugates often use disperse and/or achiral polymers with limited functionality. The heterogeneity of such conjugates may lead to manufacturing variability, poorly controlled biological performance, and limited ability to optimize structure-property relationships. Here, using insulin as a model therapeutic polypeptide, we introduce a strategy for the synthesis of polymer-protein conjugates based on discrete, chiral polymers synthesized through iterative exponential growth (IEG). These conjugates eliminate manufacturing variables originating from polymer dispersity and poorly controlled absolute configuration. Moreover, they offer tunable molecular features, such as conformational rigidity, that can be modulated to impact protein function, enabling faster or longer-lasting blood glucose responses in diabetic mice when compared to PEGylated insulin and the commercial insulin variant Lantus. Furthermore, IEG-insulin conjugates showed no signs of decreased activity, immunogenicity, or toxicity following repeat dosing. This work represents a significant step toward the synthesis of precise synthetic polymer-biopolymer conjugates and reveals that fine tuning of synthetic polymer structure may be used to optimize such conjugates in the future.

The synthesis of novel polysilylethers via entropy-driven ring-opening metathesis polymerization (ED-ROMP) of cyclic bifunctional silyl ether-based monomers is reported. These polymers display good thermal stability and ultra-low T g the cleavage of the silicon-oxygen linkages with acid or fluoride triggers, and they were partially depolymerizable by the addition of exogenous metathesis catalyst. Analysis of the deconstructed polymer products provided insight into the polymer microstructure, showing that the ED-ROMP process was regiorandom. Altogether, this work offers a new class of deconstructable polymers with a range of potential applications.via the cleavage of the silicon-oxygen linkages with acid or fluoride triggers, and they were partially depolymerizable by the addition of exogenous metathesis catalyst. Analysis of the deconstructed polymer products provided insight into the polymer microstructure, showing that the ED-ROMP process was regiorandom. Altogether, this work offers a new class of deconstructable polymers with a range of potential applications.

The immobilization of homogeneous catalysts onto supports to improve recyclability while maintaining catalytic efficiency is often a trial-and-error process limited by poor control of the local catalyst environment and few strategies to append catalysts to support materials. Here, we introduce a modular heterogenous catalysis platform that addresses these challenges. Our approach leverages the well-defined interiors of self-assembled Pd 12 L 24 metal-organic cages/polyhedra (MOCs): simple mixing of a catalyst-ligand of choice with a polymeric ligand, spacer ligands, and a Pd salt induces self-assembly of Pd 12 L 24 -cross-linked polymer gels featuring endohedrally catalyst-functionalized junctions. Semi-empirical calculations show that catalyst incorporation into the MOC junctions of these materials has minimal affect on the MOC geometry, giving rise to well-defined nanoconfined catalyst domains as confirmed experimentally using several techniques. Given the unique network topology of these freestanding gels, they are mechanically robust regardless of their endohedral catalyst composition, allowing them to be physically manipulated and transferred from one reaction to another to achieve multiple rounds of catalysis. Moreover, by decoupling the catalyst environment (interior of MOC junctions) from the physical properties of the support (the polymer matrix), this strategy enables catalysis in environments where homogeneous catalyst analogues are not viable, as demonstrated for the Au(I)-catalyzed cyclization of 4-pentynoic acid in aqueous media.

Polymer electrolytes are promising candidates for the next generation lithium-ion battery technology. Large scale screening of polymer electrolytes is hindered by the significant cost of molecular dynamics (MD) simulation in amorphous systems: the amorphous structure of polymers requires multiple, repeated sampling to reduce noise and the slow relaxation requires long simulation time for convergence. Here, we accelerate the screening with a multi-task graph neural network that learns from a large amount of noisy, unconverged, short MD data and a small number of converged, long MD data. We achieve accurate predictions of 4 different converged properties and screen a space of 6247 polymers that is orders of magnitude larger than previous computational studies. Further, we extract several design principles for polymer electrolytes and provide an open dataset for the community. Our approach could be applicable to a broad class of material discovery problems that involve the simulation of complex, amorphous materials., (© 2022. The Author(s).)

Chirality and molecular conformation are central components of life: biological systems rely on stereospecific interactions between discrete (macro)molecular conformers, and the impacts of stereochemistry and rigidity on the properties of small molecules and biomacromolecules have been intensively studied. Nevertheless, how these features affect the properties of synthetic macromolecules has received comparably little attention. Here we leverage iterative exponential growth and ring-opening metathesis polymerization to produce water-soluble, chiral bottlebrush polymers (CBPs) from two enantiomeric pairs of macromonomers of differing rigidity. Remarkably, CBPs with conformationally flexible, mirror image side chains show several-fold differences in cytotoxicity, cell uptake, blood pharmacokinetics and liver clearance; CBPs with comparably rigid, mirror image side chains show no differences. These observations are rationalized with a simple model that correlates greater conformational freedom with enhanced chiral recognition. Altogether, this work provides routes to the synthesis of chiral nanostructured polymers and suggests key roles for stereochemistry and conformational rigidity in the design of future biomaterials., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Polymers are stochastic materials that represent distributions of different molecules. In general, to quantify the distribution, polymer researchers rely on a series of chemical characterizations that each reveal partial information on the distribution. However, in practice, the exact set of characterizations that are carried out, as well as how the characterization data are aggregated and reported, is largely nonstandard across the polymer community. This scenario makes polymer characterization data highly disparate, thereby significantly slowing down the development of polymer informatics. In this work, a proposal on how structural characterization data can be organized is presented. To ensure that the system can apply universally across the entire polymer community, the proposed schema, PolyDAT, is designed to embody a minimal congruent set of vocabulary that is common across different domains. Unlike most chemical schemas, where only data pertinent to the species of interest are included, PolyDAT deploys a multi-species reaction network construct, in which every characterization on relevant species is collected to provide the most comprehensive profile on the polymer species of interest. Instead of maintaining a comprehensive list of available characterization techniques, PolyDAT provides a handful of generic templates, which align closely with experimental conventions and cover most types of common characterization techniques. This allows flexibility for the development and inclusion of new measurement methods. By providing a standard format to digitalize data, PolyDAT serves not only as an extension to BigSMILES that provides the necessary quantitative information but also as a standard channel for researchers to share polymer characterization data.

Ring-opening metathesis polymerization of norbornene-based (macro)monomers is a powerful approach for the synthesis of macromolecules with diverse compositions and complex architectures. Nevertheless, a fundamental limitation of polymers prepared by this strategy is their lack of facile degradability, limiting their utility in a range of applications. Here we describe a class of readily available bifunctional silyl ether-based cyclic olefins that copolymerize efficiently with norbornene-based (macro)monomers to provide copolymers with backbone degradability under mildly acidic aqueous conditions and degradation rates that can be tuned over several orders of magnitude, depending on the silyl ether substituents. These monomers can be used to manipulate the in vivo biodistribution and clearance rate of polyethylene glycol-based bottlebrush polymers, as well as to synthesize linear, bottlebrush and brush-arm star copolymers with degradable segments. We expect that this work will enable preparation of degradable polymers by ROMP for biomedical applications, responsive self-assembly and improved sustainability.

Nitroxides occupy a privileged position among plausible metal-free magnetic resonance imaging (MRI) contrast agents (CAs) due to their inherently low-toxicity profiles; nevertheless, their translational development has been hindered by a lack of appropriate contrast sensitivity. Nanostructured materials with high nitroxide densities, where each individual nitroxide within a macromolecular construct contributes to the image contrast, could address this limitation, but the synthesis of such materials remains challenging. Here, we report a modular and scalable synthetic approach to nitroxide-based brush-arm star polymer (BASP) organic radical CAs (ORCAs) with high nitroxide loadings. The optimized ∼30 nm diameter "BASP-ORCA3" displays outstanding T 2 sensitivity with a very high molecular transverse relaxivity ( r 2 > 1000 mM -1 s -1 ). BASP-ORCA3 further exhibits excellent stability in vivo, no acute toxicity, and highly desirable pharmacokinetic and biodistribution profiles for longitudinal detection of tumors by MRI. When injected intravenously into mice bearing subcutaneous plasmacytomas, BASP-ORCA3 affords distinct in vivo visualization of tumors on translationally relevant time scales. Leveraging its high sensitivity, BASP-ORCA3 enables efficient mapping of tumor necrosis, which is an important biomarker to predict therapeutic outcomes. Moreover, BASP-ORCA3 allows for detection of millimetric tumor implants in a disseminated murine model of advanced-stage human ovarian cancer that possess genetic, histological, and vascular characteristics that are similar to those seen in patients. This work establishes BASP-ORCA3 as a promising metal-free spin contrast agent for MRI.

Deciphering the significance of length, sequence, and stereochemistry in block copolymer self-assembly remains an ongoing challenge. A dearth of methods to access uniform block co-oligomers/polymers with precise stereochemical sequences has precluded such studies. Here, we develop iterative exponential growth methods for the synthesis of a small library of unimolecular stereoisomeric diblock 32-mers. X-ray scattering reveals that stereochemistry modulates the phase behavior of these polymers, which we rationalize based on simulations carried out on a theoretical model system. This work demonstrates that stereochemical sequence can play a crucial role in unimolecular polymer self-assembly.

We report star polymer metal-organic cage (polyMOC) materials whose structures, mechanical properties, functionalities, and dynamics can all be precisely tailored through a simple three-component assembly strategy. The star polyMOC network is composed of tetra-arm star polymers functionalized with ligands on the chain ends, small molecule ligands, and palladium ions; polyMOCs are formed via metal-ligand coordination and thermal annealing. The ratio of small molecule ligands to polymer-bound ligands determines the connectivity of the MOC junctions and the network structure. The use of large M 12 L 24 MOCs enables great flexibility in tuning this ratio, which provides access to a rich spectrum of material properties including tunable moduli and relaxation dynamics., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report the synthesis of Janus bottlebrush block copolymers by graft-through polymerization of branched diblock macromonomers. Self-assembly of the bottlebrushes was characterized by small-angle X-ray scattering, atomic force microscopy, and scanning electron microscopy. Phase separation and packing models of the bottlebrushes were computed, and their self-assembly behavior was corroborated experimentally in bulk and in thin films. Lamellar, hexagonal cylinder, and gyroid phases were observed and modeled. The A-branch-B Janus bottlebrush structure provides several unique advantages in the context of bottlebrush polymer assembly, including access to the first examples of gyroid phases.

Gels formed via metal-ligand coordination typically have very low branch functionality, f, as they consist of ∼2-3 polymer chains linked to single metal ions that serve as junctions. Thus, these materials are very soft and unable to withstand network defects such as dangling ends and loops. We report here a new class of gels assembled from polymeric ligands and metal-organic cages (MOCs) as junctions. The resulting 'polyMOC' gels are precisely tunable and may feature increased branch functionality. We show two examples of such polyMOCs: a gel with a low f based on a M2L4 paddlewheel cluster junction and a compositionally isomeric one of higher f based on a M12L24 cage. The latter features large shear moduli, but also a very large number of elastically inactive loop defects that we subsequently exchanged for functional ligands, with no impact on the gel's shear modulus. Such a ligand substitution is not possible in gels of low f, including the M2L4-based polyMOC.

Chemists have long sought sequence-controlled synthetic polymers that mimic nature's biopolymers, but a practical synthetic route that enables absolute control over polymer sequence and structure remains a key challenge. Here, we report an iterative exponential growth plus side-chain functionalization (IEG+) strategy that begins with enantiopure epoxides and facilitates the efficient synthesis of a family of uniform >3 kDa macromolecules of varying sequence and stereoconfiguration that are coupled to produce unimolecular polymers (>6 kDa) with sequences and structures that cannot be obtained using traditional polymerization techniques. Selective side-chain deprotection of three hexadecamers is also demonstrated, which imbues each compound with the ability to dissolve in water. We anticipate that these new macromolecules and the general IEG+ strategy will find broad application as a versatile platform for the scalable synthesis of sequence-controlled polymers.

Stimuli-responsive multimodality imaging agents have broad potential in medical diagnostics. Herein, we report the development of a new class of branched-bottlebrush polymer dual-modality organic radical contrast agents--ORCAFluors--for combined magnetic resonance and near-infrared fluorescence imaging in vivo. These nitroxide radical-based nanostructures have longitudinal and transverse relaxation times that are on par with commonly used heavy-metal-based magnetic resonance imaging (MRI) contrast agents. Furthermore, these materials display a unique compensatory redox response: fluorescence is partially quenched by surrounding nitroxides in the native state; exposure to ascorbate or ascorbate/glutathione leads to nitroxide reduction and a concomitant 2- to 3.5-fold increase in fluorescence emission. This behaviour enables correlation of MRI contrast, fluorescence intensity and spin concentration with tissues known to possess high concentrations of ascorbate in mice. Our in vitro and in vivo results, along with our modular synthetic approach, make ORCAFluors a promising new platform for multimodality molecular imaging.

This report describes the synthesis of miktoarm brush-arm star polymers (BASPs) from branched and linear norbornene-terminated macromonomers (MMs) via the brush-first ring-opening metathesis polymerization (ROMP) method. First, a polystyrene (PS)-branch-poly(lactic acid) (PLA) MM is synthesized via a combination of atom transfer radical polymerization (ATRP), tin(II)-mediated ring opening polymerization, and copper-catalyzed azide-alkyne cycloaddition reactions. Graft-through ROMP of this MM followed by in situ cross-linking with a photo-cleavable bis-norbornene derivative provided nanoscopic BASPs with photodegradable cores and a precise 1:1 PS:PLA arm composition. Three-miktoarm BASPs are prepared in an analogous manner via copolymerization of the same PS-branch-PLA MM with a poly(ethylene glycol) (PEG) MM prior to cross-linking. Intramolecular phase segregation of these miktoarm BASPs is characterized by transmission electron microscopy (TEM); a UV-induced structural rearrangement from three-faced Janus particles to micelles is observed., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bifunctional, fluorinated cyclooctynes were used for the in situ "click" crosslinking of azide-terminated photodegradable star polymers, yielding photodegradable polymeric model networks with well-defined structures and tunable gelation times.

A simple scheme involving atom transfer radical polymerization (ATRP) from a bifunctional initiator, conversion of the bromine end groups of the resulting telechelic polymer to azides, and cross-linking of this azido-telechelic macromonomer with multi-acetylene functionalized small molecules via copper-catalyzed azide-alkyne cycloaddition was employed to prepare the first tert-butyl acrylate model networks. This general scheme is wide in scope, enabling synthesis of model networks possessing defined pore size from any monomer polymerizable by ATRP. Introduction of an olefin moiety into the ATRP initiator enabled degradation of the materials by ozonolysis to yield star polymer products bearing three or four arms depending on which cross-linker was employed in the parent network. Size-exclusion chromatography of the ozonolysis products confirmed the pore size of the parent network and yielded insight into the number of unreacted functionalities. Model networks derived from a trifunctional alkyne were found to be more completely cross-linked than those derived from a tetrafunctional alkyne, presumably due to less steric hindrance in the former system.

Polyethylene (PE) is the most widely produced synthetic polymer. By installing chemically cleavable bonds into the backbone of PE, it is possible to produce chemically deconstructable PE derivatives; to date, however, such designs have primarily relied on carbonyl‐ and olefin‐related functional groups. Bifunctional silyl ethers (BSEs; SiR2(OR′2)) could expand the functional scope of PE mimics as they possess strong Si−O bonds and facile chemical tunability. Here, we report BSE‐containing high‐density polyethylene (HDPE)‐like materials synthesized through a one‐pot catalytic ring‐opening metathesis polymerization (ROMP) and hydrogenation sequence. The crystallinity of these materials can be adjusted by varying the BSE concentration or the steric bulk of the Si‐substituents, providing handles to control thermomechanical properties. Two methods for chemical recycling of HDPE mimics are introduced, including a circular approach that leverages acid‐catalyzed Si−O bond exchange with 1‐propanol. Additionally, despite the fact that the starting HDPE mimics were synthesized by chain‐growth polymerization (ROMP), we show that it is possible to recover the molar mass and dispersity of recycled HDPE products using step‐growth Si−O bond formation or exchange, generating high molecular weight recycled HDPE products with mechanical properties similar to commercial HDPE. [ABSTRACT FROM AUTHOR]

Polymer networks, which are materials composed of many smaller components—referred to as "junctions" and "strands"—connected together via covalent or non‐covalent/supramolecular interactions, are arguably the most versatile, widely studied, broadly used, and important materials known. From the first commercial polymers through the plastics revolution of the 20th century to today, there are almost no aspects of modern life that are not impacted by polymer networks. Nevertheless, there are still many challenges that must be addressed to enable a complete understanding of these materials and facilitate their development for emerging applications ranging from sustainability and energy harvesting/storage to tissue engineering and additive manufacturing. Here, we provide a unifying overview of the fundamentals of polymer network synthesis, structure, and properties, tying together recent trends in the field that are not always associated with classical polymer networks, such as the advent of crystalline "framework" materials. We also highlight recent advances in using molecular design and control of topology to showcase how a deep understanding of structure–property relationships can lead to advanced networks with exceptional properties. [ABSTRACT FROM AUTHOR]

The properties of polymeric materials are dictated not only by their composition but also by their molecular architecture. Here, by employing brush‐first ring‐opening metathesis polymerization (ROMP), norbornene‐terminated poly(ethylene oxide) (PEO) macromonomers (MM‐n, linear architecture), bottlebrush polymers (Brush‐n, comb architecture), and brush‐arm star polymers (BASP‐n, star architecture), where n indicates the average degree of polymerization (DP) of PEO, are synthesized. The impact of architecture on the thermal properties and Li+ conductivities for this series of PEO architectures is investigated. Notably, in polymers bearing PEO with the highest degree of polymerization, irrespective of differences in architecture and molecular weight (~100‐fold differences), electrolytes with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as an Li+ source exhibit normalized ionic conductivities (σn) within only 4.9 times difference (σn = 29.8 × 10−5 S cm−1 for MM‐45 and σn = 6.07 × 10−5 S cm−1 for BASP‐45) at a concentration of Li+r = [Li+]/[EO] = 1/12 at 50 °C. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 448–455 Brush‐first ring‐opening metathesis polymerization (ROMP) provides norbornene‐terminated macromonomers (linear architecture), bottlebrush polymers (comb architecture), and brush‐arm star polymers (BASPs) (star architecture) with varied lengths of poly(ethylene oxide) (PEO) chains. The impact of those distinct PEO architectures on thermal properties and Li+ conductivity is investigated. Notably, these polymers with varied architectures are derived from the same components. [ABSTRACT FROM AUTHOR]

Gels made of telechelic polymers connected by reversible cross-linkers are a versatile design platform for biocompatible viscoelastic materials. Their linear response to a step strain displays a fast, near-exponential relaxation when using low-valence cross-linkers, while larger supramolecular cross-linkers bring about much slower dynamics involving a wide distribution of timescales whose physical origin is still debated. Here, we propose a model where the relaxation of polymer gels in the dilute regime originates from elementary events in which the bonds connecting two neighboring cross-linkers all disconnect. Larger cross-linkers allow for a greater average number of bonds connecting them but also generate more heterogeneity. We characterize the resulting distribution of relaxation timescales analytically and accurately reproduce stress relaxation measurements on metal-coordinated hydrogels with a variety of cross-linker sizes including ions, metal-organic cages, and nanoparticles. Our approach is simple enough to be extended to any cross-linker size and could thus be harnessed for the rational design of complex viscoelastic materials. [ABSTRACT FROM AUTHOR]

The mechanical properties of covalent polymer networks often arise from the permanent end-linking or cross-linking of polymer strands, and molecular linkers that break more easily would likely produce materials that require less energy to tear. We report that cyclobutane-based mechanophore cross-linkers that break through force-triggered cycloreversion lead to networks that are up to nine times as tough as conventional analogs. The response is attributed to a combination of long, strong primary polymer strands and cross-linker scission forces that are approximately fivefold smaller than control cross-linkers at the same timescales. The enhanced toughness comes without the hysteresis associated with noncovalent cross-linking, and it is observed in two different acrylate elastomers, in fatigue as well as constant displacement rate tension, and in a gel as well as elastomers. [ABSTRACT FROM AUTHOR]

We explore the morphology and phase behavior of branched diblock macromonomers and their polymers. A series of macromonomers was synthesized based on a disubstituted norbornene. The first branch consists of polydimethylsiloxane (PDMS) while the second branch is a quasi-mesogenic structure incorporating one or more cyanobiphenyl (CB) moieties. Bottlebrush polymers with varying degrees of polymerization were prepared by "graft-through" ring-opening metathesis of the macromonomers. The molecules in the resulting library of macromonomers and bottlebrush polymers self-assemble to form classically observed microphase-separated structures, including spheres, hexagonally packed cylinders, bicontinuous gyroid, and lamellae. The systematic variation of molecular structure, molecular weight of each branch, and degree of polymerization of the polymers results in a diverse set of structures and properties. We report the observation of well-ordered lamellae and cylinders with d-spacings as low as 6.1 and 8.0 nm, respectively. The system displays an asymmetric phase diagram, with large deviations from the canonical phase behavior of linear coil-coil diblocks. Hexagonally packed cylinders and lamellae are observed at remarkably small mass fractions of the mesogen-containing block of 0.07 and 0.21, respectively. The samples are highly birefringent, and polarized optical microscopy revealed the formation of well-developed textures in microphase-separated states formed by cooling samples through the order-disorder transition. The textures are reminiscent of the classic fan-like or focal-conic textures observed in small molecule liquid crystal mesophases, highlighting the formation of unusually large and well-ordered grains of the microphase-separated PDMS and CB microdomains. Apparent crystallization of the CB units in systems with two or three CB moieties per monomer results in distortion of the microphase-separated structure. The small d-spacings and large grain sizes observed here highlight the versatility and potential utility of this molecular architecture for designing and engineering new functional materials. [ABSTRACT FROM AUTHOR]

The synthesis of polymer therapeutics capable of controlled loading and synchronized release of multiple therapeutic agents remains a formidable challenge in drug delivery and synthetic polymer chemistry. Herein, we report the synthesis of polymer nanoparticles (NPs) that carry precise molar ratios of doxorubicin, camptothecin, and cisplatin. To our knowledge, this work provides the first example of orthogonally triggered release of three drugs from single NPs. The highly convergent synthetic approach opens the door to new NP-based combination therapies for cancer. [ABSTRACT FROM AUTHOR]

Spin-labeled polylactide brush polymers were synthesized via ring-opening metathesis polymerization (ROMP), and nitroxide radicals were incorporated at three different locations of brush polymers: the end and the middle of the backbone, and the end of the side chains (periphery). Electron paramagnetic resonance (EPR) was used to quantitatively probe the macromolecular structure of brush polymers in dilute solutions. The peripheral spin-labels showed significantly higher mobility than the backbone labels, and in dimethylsulfoxide (DMSO), the backbone end labels were shown to be more mobile than the middle labels. Reduction of the nitroxide labels by a polymeric reductant revealed location-dependent reactivity of the nitroxide labels: peripheral nitroxides were much more reactive than the backbone nitroxides. In contrast, almost no difference was observed when a small molecule reductant was used. These results reveal that the dense side chains of brush polymers significantly reduce the interaction of the backbone region with external macromolecules, but allow free diffusion of small molecules. [ABSTRACT FROM AUTHOR]