SciCombinator

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Concept: Copolymer

173

Polymersomes, made up of amphiphilic block copolymers, are emerging as a powerful tool in drug delivery and synthetic biology due to their high stability, chemical versatility, and surface modifiability. The full potential of polymersomes, however, has been hindered by a lack of versatile methods for shape control. Here we show that a range of non-spherical polymersome morphologies with anisotropic membranes can be obtained by exploiting hydrophobic directional aromatic interactions between perylene polymer units within the membrane structure. By controlling the extent of solvation/desolvation of the aromatic side chains through changes in solvent quality, we demonstrate facile access to polymersomes that are either ellipsoidal or tubular-shaped. Our results indicate that perylene aromatic interactions have a great potential in the design of non-spherical polymersomes and other structurally complex self-assembled polymer structures.

Concepts: Polymer chemistry, Copolymer, Cell membrane, Structure, Polymer

138

Polyglycerol is an attractive hydrophilic building block of amphiphilic copolymers for biomedical and pharmaceutical applications due to its biocompatibility, facile chemical modification, and anti-fouling activity. Herein we introduce theranostic nanoemulsions incorporating anti-cancer therapeutic and contrast agents using linear polyglycerol-poly(ε-caprolactone) diblock copolymers (PG-b-PCL). Lipiodol is used as a core oil that dissolves paclitaxel and serves as a contrast agent for computer tomography (CT).

Concepts: Agent, Magnetic resonance imaging, Solubility, Contrast, Contrast medium, Radiography, Copolymer, Medical imaging

137

Reported herein is the development of an effective strategy for controlled and efficient Lewis pair polymerization of conjugated polar alkenes, including methyl methacrylate (MMA),n-butyl methacrylate (nBuMA), and γ-methyl-α-methylene-γ-butyrolactone (γMMBL), by the utilization of sterically encumbered Al(BHT)₂Me (BHT: 2,6-di-tert-butyl-4-methylphenol) as a Lewis acid that shuts down intramolecular backbiting termination. In combination with a selectedN-heterocyclic carbene (NHC) as a Lewis base, the polymerization of MMA exhibited activity up to 3000 h-1TOF and an acceptable initiation efficiency of 60.6%, producing polymers with high molecular weight (Mnup to 130 kg/mol) and extremely narrow dispersity (Đ= 1.06~1.13). This controlled polymerization with a living characteristic has been evidenced by chain-extension experiments and chain-end analysis, and enabled the synthesis of well-defined diblock copolymers.

Concepts: Gilbert N. Lewis, Polymer, Steric effects, Random coil, Copolymer

29

The ability to synthesize a diverse spectrum of one-dimensional (1D) nanocrystals presents an enticing prospect for exploring nanoscale size- and shape-dependent properties. Here we report a general strategy to craft a variety of plain nanorods, core-shell nanorods, and nanotubes with precisely controlled dimensions and compositions by capitalizing on functional bottlebrush-like block copolymers with well-defined structures and narrow molecular weight distributions as nanoreactors. These cylindrical unimolecular nanoreactors enable a high degree of control over the size, shape, architecture, surface chemistry, and properties of 1D nanocrystals. We demonstrate the synthesis of metallic, ferroelectric, upconversion, semiconducting, and thermoelectric 1D nanocrystals, among others, as well as combinations thereof.

Concepts: Synthesis, Copolymer, Polymer chemistry, Molecule, Physics, Dimension, Vector space, Space

28

AB diblock copolymers were prepared by sequential ring-opening metathesis polymerization of cyclooctenes catalyzed by a Ru-based Grubbs catalyst. The relatively slow polymerization of cis-3-phenylcyclooct-1-ene (3PC) or cis-cyclooct-2-en-1-yl acetate (3AC) was first carried out and then followed by the faster polymerization of unsubstituted cis-cyclooctene (COE) from the active Ru-alkylidene chain ends. In contrast, simultaneous polymerization of the two monomers provides copolymers with a statistical monomer distribution owing to extensive chain transfer. The resulting poly(3PC-b-COE) and poly(3AC-b-COE) diblock copolymers were subjected to hydrogenation to selectively saturate the backbone alkenes. The consequences of architectural variance between the materials from simultaneous vs. sequential polymerizations are reflected by the contrasting thermal characteristics.

Concepts: Hydrogen, Catalysis, Monomer, Copolymer, Polymerization, Olefin metathesis, Polymer chemistry, Polymer

28

The purpose of the study was to investigate and identify the interactions within solid dispersions of cationic drugs and anionic polymers processed by hot-melt extrusion (HME) technique. Propranolol HCl (PRP) and diphenhydramine HCl (DPD) were used as model cationic active substances while pH sensitive anionic methacrylic acid based methyl methacrylate copolymers Eudragit L100® (L100) and ethyl acrylate copolymer Eudragit L100-55 (Acryl EZE) (L100-55) were used as polymeric carriers. The extrudates were further characterized using various physicochemical characterization techniques to determine the morphology, the drug state within the polymer matrices and the type of drug - polymer interactions. Molecular modelling predicted the existence of two possible H-bonding types while the X - ray photon spectroscopy (XPS) advanced surface analysis of the extrudates revealed intermolecular ionic interactions between the API amino functional groups and the polymer carboxylic groups through the formation of hydrogen bonding. The magnitude of the intermolecular interactions varied according to the drug - polymer miscibility.

Concepts: Polymer chemistry, Protein, Copolymer, Hydrogen, Functional group, Functional groups, Carboxylic acid, Polymer

28

Although biodegradable polymers have found extensive applications in medical areas, there are limited reports that show elastomeric behavior. In this work, a biodegradable, elastomeric polymer is demonstrated from a four-armed star copolymer. With a fixed middle core composition, comprising caprolactone (CL) and L-lactide (LA), an elastomer is obtained by increasing the polylactide (PLA) end block lengths to obtain sufficient end block crystallinity. This increase suppressed the middle core’s crystallinity yet ensured cocrystallization of the PLA ends of individual star copolymer chains to form a three-dimensional network via physical crosslinking. Cyclic and creep test of the star copolymers showed that at least 75% of recovery was achieved. Degradation study of the copolymer showed that degradation first occurred in the caprolactone-co-lactide (CLLA) core, followed by degradation in the PLA ends. Chain scission in the middle core resulted in immediate formation of CL crystals within the core and increased crystallinity over time, in both CLLA core and PLA ends. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 100A:3436-3445, 2012.

Concepts: Cross-link, Materials science, Copolymer, Thermoplastic, Polybutadiene, Polymer chemistry, Elastomer, Polymer

28

Nanocomposites, composed of organic and inorganic building blocks, can combine the properties from the parent constituents and generate new properties to meet current and future demands in functional materials. Recent developments in nanoparticle synthesis provide a plethora of inorganic building blocks, building the foundation for constructing hybrid nanocomposites with unlimited possibilities. The properties of nanocomposite materials depend not only on those of individual building blocks but also on their spatial organization at different length scales. Block copolymers, which microphase separate into various nanostructures, have shown their potential for organizing inorganic nanoparticles in bulk/thin films. Block copolymer-based supramolecules further provide more versatile routes to control spatial arrangement of the nanoparticles over multiple length scales. This review provides an overview of recent efforts to control the hierarchical assemblies in block copolymer-based hybrid nanocomposites.

Concepts: Polymer chemistry, Copolymer, Organic compound, Nanoparticle, Nanocomposite, Polymer, Nanomaterials

28

Two kinds of core-shell structured multifunctional nanocarriers of gold nanoclusters (Au NCs) as core and folate (FA)-conjugated amphiphilic hyperbranched block copolymer as shell based on poly(l-lactide) (PLA) inner arm and FA-conjugated sulfated polysaccharide (GPPS-FA) outer arm (Au NCs-PLA-GPPS-FA) were synthesized for targeted anticancer drug delivery. The structure and properties of Au NCs-PLA-GPPS-FA copolymers were characterized and determined by (1)H NMR spectrum, FT-IR spectra, dynamic light scattering (DLS), fluorescence spectroscopy, and transmission electron microscopic (TEM) analyses. The anticancer drug, camptothecin (CPT) was used as a hydrophobic model anticancer drug. In vitro, two kinds of the nanocarriers presented a relatively rapid release in the first stage (up to 1 h) followed by a sustained release period (up to 15 h), and then reached a plateau at pH 5.3, 7.4, and 9.6. The release results indicated that CPT release from two kinds of the nanocarriers at pH 9.6 was much greater than that at both pH 5.3 and 7.4. The cytotoxicity studies showed that the CPT-loaded nanocarriers provided high anticancer activity against Hela cells. Furthermore, nanocarriers gained specificity to target some cancer cells because of the enhanced cell uptake mediated by FA moiety. The fluorescent images studies showed that the nanocarriers could track at the cellular level for advance therapy. The results indicated that the Au NCs-PLA-GPPS-FA copolymers not only had great potential as tumor-targeted drug delivery carrier, but also had an assistant role in the treatment of cancer.

Concepts: Dynamic light scattering, Cancer, Copolymer, Fluorescence, Polymer, Spectroscopy

27

A diblock copolymer constituting of a poly(ethylene glycol) (PEG) and a polycaprolactone (PCL) segment, linked with a pH-sensitive hydrazone bond (Hyd), was synthesized. Micelles formed from this copolymer, offer the advantage of encapsulating hydrophobic drugs without the need for conjugation sites. All synthesized polymers were characterised using gel permeation chromatography, infrared and proton nuclear spectroscopies. PEG-Hyd-PCL micelles were prepared using the solvent-displacement method and α-Tocopherol was used as a model drug due to its high hydrophobicity. The micelle size and drug loading efficiency were studied with regards to the hydrophilic ratio, f, molecular weight, and the polymer/drug ratio. Dynamic light scattering and transmission electron microscopy showed that the PEG-Hyd-PCL micelles had sizes ranging from 50 to 200nm. Aqueous micellar dispersions exhibited significantly higher values of turbidity in mildy acidic pH than in neutral, indicating pH-sensitivity for the PEG-Hyd-PCL micelles. The zeta potential of the micellar solutions decreased and the molecular weight distribution became bimodal at mildly acidic pH also supporting the pH sensitive properties of the copolymer. The critical micelle concentration was calculated using fluorescence spectroscopy.

Concepts: Critical micelle concentration, Copolymer, Chemical properties, Hydrophobic effect, Spectroscopy, Micelle, Electron, Colloidal chemistry