Browse
Submit Data
Databases
API
Help

Dataset Information

24 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Synthetic Strategy for Preparing Chiral Double-semicrystalline Polyether Block Copolymers.

ABSTRACT: We report an effective strategy for the synthesis of semi-crystalline block copolyethers with well-defined architecture and stereochemistry. As an exemplary system, triblock copolymers containing either atactic (racemic) or isotactic (R or S) poly(propylene oxide) end blocks with a central poly(ethylene oxide) mid-block were prepared by anionic ring-opening procedures. Stereochemical control was achieved by an initial hydrolytic kinetic resolution of racemic terminal epoxides followed by anionic ring-opening polymerization of the enantiopure monomer feedstock. The resultant triblock copolymers were highly isotactic (meso triads [mm]% ~ 90%) with optical microscopy, differential scanning calorimetry, wide angle x-ray scattering and small angle x-ray scattering being used to probe the impact of the isotacticity on the resultant polymer and hydrogel properties.

SUBMITTER: McGrath AJ

PROVIDER: S-EPMC4408015 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Synthetic Strategy for Preparing Chiral Double-semicrystalline Polyether Block Copolymers.

McGrath Alaina J AJ Shi Weichao W Rodriguez Christina G CG Kramer Edward J EJ Hawker Craig J CJ Lynd Nathaniel A NA

Polymer chemistry 20150301 9

We report an effective strategy for the synthesis of semi-crystalline block copolyethers with well-defined architecture and stereochemistry. As an exemplary system, triblock copolymers containing either atactic (racemic) or isotactic (R or S) poly(propylene oxide) end blocks with a central poly(ethylene oxide) mid-block were prepared by anionic ring-opening procedures. Stereochemical control was achieved by an initial hydrolytic kinetic resolution of racemic terminal epoxides follo ...[more]

PMID: 25914726

Similar Datasets

Semicrystalline Block Copolymers in Rigid Confining Nanopores.

Project description:We have investigated PLLA crystallization in lamellae-forming PS-b-PLLA confined to straight cylindrical nanopores under weak confinement (nanopore diameter D/equilibrium PS-b-PLLA period L0 ? 4.8). Molten PS-b-PLLA predominantly forms concentric lamellae along the nanopores, but intertwined helices occur even for D/L0 ? 7.3. Quenching PS-b-PLLA melts below TG(PS) results in PLLA cold crystallization strictly confined by the vitrified PS domains. Above TG(PS), PLLA crystallization is templated by the PS-b-PLLA melt domain structure in the nanopore centers, while adsorption on the nanopore walls stabilizes the outermost cylindrical PS-b-PLLA shell. In between, the nanoscopic PS-b-PLLA melt domain structure apparently ripens to reduce frustrations transmitted from the outermost immobilized PS-b-PLLA layer. The onset of PLLA crystallization catalyzes the ripening while transient ripening states are arrested by advancing PLLA crystallization. Certain helical structure motifs persist PLLA crystallization even if PS is soft. The direction of fastest PLLA crystal growth is preferentially aligned with the nanopore axes to the same degree as for PLLA homopolymer, independent of whether PS is vitreous or soft.

| S-EPMC6114844 | biostudies-literature

Synthesis and Characterization of N-Substituted Polyether-Block-Amide Copolymers.

Project description:A series of N-substituted polyether-block-amide (PEBA-X%) copolymers were prepared by melt polycondensation of nylon-6 prepolymer and polytetramethylene ether glycol at an elevated temperature using titanium isopropoxide as a catalyst. The structure, thermal properties, and crystallinity of PEBA-X% were investigated using nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry, wide angle X-ray diffraction, and thermogravimetric analysis. In general, the crystallinity, melting point, and thermal degradation temperature of PEBA-X% decreased as the incorporation of N-methyl functionalized groups increased, owing to the disruption caused to the structural regularity of the copolymer. However, in N-acetyl functionalized analogues, the crystallinity first dropped and then increased because of a new γ form arrangement that developed in the microstructure. After the cross-linking reaction of the N-methyl-substituted derivative, which has electron-donating characteristics, with poly(4,4'-methylenebis(phenyl isocyanate), the decomposition temperature of the resulting polymer significantly increased, whereas no such improvements could be observed in the case of the electro-withdrawing N-acetyl-substituted derivative, because of the incompleteness of its cross-linking reaction.

| S-EPMC7915099 | biostudies-literature

Moebius strips of chiral block copolymers.

Project description:The Moebius topology (twisted, single-sided strip) is intriguing because of its structural elegance and distinct properties. Here we report the generation of block copolymer Moebius strips via a fast self-assembly of chiral block copolymer polystyrene-block-poly(D-lactide acid) (PS-b-PDLA) in tetrahydrofuran/water mixed solvents. The Moebius strip is formed by morphological evolution from large compound micelle (LCM) to spindle-like micelle (SLM) and then to toroid with a 180° twist along the ring. Mechanism insight reveals that a subtle balance of crystallization of PDLA and microphase separation between PS and PDLA chains dominates the formation of Moebius strips. An intriguing helix-helix transition occurs during the chiral transfer from microphase to assemblies, which is driven by relaxation of the internal stress within SLM related to orientated stretching of PS chains. Mesoporous chiral channels can be generated within Moebius strips after removal of PDLA, which are interesting in chiral recognition, separation and asymmetric catalysis.

| S-EPMC6733789 | biostudies-literature

Curvature-coupled hydration of Semicrystalline Polymer Amphiphiles yields flexible Worm Micelles but favors rigid Vesicles: polycaprolactone-based block copolymers.

Project description:Crystallization processes are in general sensitive to detailed conditions, but our present understanding of underlying mechanisms is insufficient. A crystallizable chain within a diblock copolymer assembly is expected to couple curvature to crystallization and thereby impact rigidity as well as preferred morphology, but the effects on dispersed phases have remained unclear. The hydrophobic polymer polycaprolactone (PCL) is semi-crystalline in bulk (T(m) = 60°C) and is shown here to generate flexible worm micelles or rigid vesicles in water from several dozen polyethyleneoxide-based diblocks (PEO-PCL). Despite the fact that `worms' have a mean curvature between that of vesicles and spherical micelles, `worms' are seen only within a narrow, process-dependent wedge of morphological phase space that is deep within the vesicle phase. Fluorescence imaging shows worms are predominantly in one of two states - either entirely flexible with dynamic thermal undulations or fully rigid; only a few worms appear rigid at room temperature (T << T(m)), indicating suppression of crystallization by both curvature and PCL hydration. Worm rigidification, which depends on molecular weight, is also prevented by copolymerization of caprolactone with just 10% racemic lactide that otherwise has little impact on bulk crystallinity. In contrast to worms, vesicles of PEO-PCL are always rigid and typically leaky. Defects between crystallite domains induce dislocation-roughening with focal leakiness although select PEO-PCL - which classical surfactant arguments would predict make worms - yield vesicles that retain encapsulant and appear smooth, suggesting a gel or glassy state. Hydration in dispersion thus tends to selectively soften high curvature microphases.

| S-EPMC3075012 | biostudies-literature

General synthetic route to cell-permeable block copolymers via ROMP.

Project description:The applications of block copolymers are myriad, ranging from electronics to functionalized resins to therapeutics. The ring-opening metathesis polymerization (ROMP) is an especially valuable reaction for block copolymer assembly because each block can be generated with length control. We sought to use this polymerization to expand the repertoire of block copolymers by implementing a strategy that involves postpolymerization modification of a backbone bearing selectively reactive groups. To this end, we demonstrate that ROMP can be used to synthesize a block copolymer scaffold that possesses three types of functional groups-a succinimidyl ester, an alpha-chloroacetamide group, and a ketone-each of which can be modified independently. Thus, a single scaffold can be elaborated to afford a wide range of block copolymers. Exploiting this synthetic approach and the length control offered by ROMP, we assemble block copolymers capable of traversing the membrane and entering mammalian cells.

| S-EPMC2750816 | biostudies-literature

A Novel Synthetic Strategy for Preparing Polyamide 6 (PA6)-Based Polymer with Transesterification.

Project description:In the polymerization of caprolactam, the stoichiometry of carboxyl groups and amine groups in the process of melt polycondensation needs to be balanced, which greatly limits the copolymerization modification of polyamide 6. In this paper, by combining the characteristics of the polyester polymerization process, a simple and flexible synthetic route is proposed. A polyamide 6-based polymer can be prepared by combining caprolactam hydrolysis polymerization with transesterification. First, a carboxyl-terminated polyamide 6-based prepolymer is obtained by a caprolactam hydrolysis polymerization process using a dibasic acid as a blocking agent. Subsequently, ethylene glycol is added for esterification to form a glycol-terminated polyamide 6-based prepolymer. Finally, a transesterification reaction is carried out to prepare a polyamide 6-based polymer. In this paper, a series of polyamide 6-based polymers with different molecular weight blocks were prepared by adjusting the amount and type of dibasic acid added, and the effects of different control methods on the structural properties of the final product are analyzed. The results showed that compared with the traditional polymerization method of polyamide 6, the novel synthetic strategy developed in this paper can flexibly design prepolymers with different molecular weights and end groups to meet different application requirements. In addition, the polyamide 6-based polymer maintains excellent mechanical and hygroscopic properties. Furthermore, the molecular weight increase in the polyamide 6 polymer is no longer dependent on the metering balance of the end groups, providing a new synthetic route for the copolymerization of polyamide 6 copolymer.

| S-EPMC6631148 | biostudies-literature

Synthesis of Amphiphilic Block Copolymers Containing Chiral Polythiophene Chains and Their Micelle Formation and Chiroptical Properties.

Project description:Amphiphilic block copolymers consisting of hydrophobic regioregular head-to-tail (HT) chiral ((S)-poly-1a-b-poly-3) or achiral (poly-1b-b-poly-3) polythiophene chains and a hydrophilic poly(acrylic acid) chain were synthesized. (S)-Poly-1a-b-poly-3 with a chiral polythiophene block formed a micelle in water that exhibited a characteristic induced circular dichroism (ICD) in the π⁻π* transition region due to the formation of supramolecular π-stacked chiral aggregates of the chiral polythiophene blocks in the core. These aggregates were stable, showing no precipitation for more than 5 days. Micelles consisting of chiral (S)-poly-1a-b-poly-3 and achiral poly-1b-b-poly-3 showed negative nonlinear effects on supramolecular chiral aggregate formation in the core. Chiral polythiophene aggregates formed in (S)-poly-1a-b-poly-3 micelle cores were stabilized by the crosslinking of poly(acrylic acid) blocks with diamines in the shell. The ICD intensity of the (S)-poly-1a-b-poly-3 micelle after shell crosslinking showed almost no change with temperature, while that before shell crosslinking decreased with increasing temperature.

| S-EPMC6404056 | biostudies-literature

Protection of Double-Stranded RNA via Complexation with Double Hydrophilic Block Copolymers: Influence of Neutral Block Length in Biologically Relevant Environments.

Project description:Interaction between the anionic phosphodiester backbone of DNA/RNA and polycations can be exploited as a means of delivering genetic material for therapeutic and agrochemical applications. In this work, quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-poly(N,N-dimethylacrylamide) (PQDMAEMA-b-PDMAm) double hydrophilic block copolymers (DHBCs) were synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization as nonviral delivery vehicles for double-stranded RNA. The assembly of DHBCs and dsRNA forms distinct polyplexes that were thoroughly characterized to establish a relationship between the length of the uncharged poly(N,N-dimethylacrylamide) (PDMA) block and the polyplex size, complexation efficiency, and colloidal stability. Dynamic light scattering reveals the formation of smaller polyplexes with increasing PDMA lengths, while gel electrophoresis confirms that these polyplexes require higher N/P ratio for full complexation. DHBC polyplexes exhibit enhanced stability in low ionic strength environments in comparison to homopolymer-based polyplexes. In vitro enzymatic degradation assays demonstrate that both homopolymer and DHBC polymers efficiently protect dsRNA from degradation by RNase A enzyme.

| S-EPMC9198985 | biostudies-literature

Synthetic Approaches for Poly(Phenylene) Block Copolymers via Nickel Coupling Reaction for Fuel Cell Applications.

Project description:Several methods to synthesize poly(phenylene) block copolymers through the nickel coupling reaction were attempted to reduce the use of expensive nickel catalysts in polymerization. The model reaction for poly(phenylene) having different types of dichlorobenzene derivative monomers illustrated the potential use of cost-effective catalysts, such as NiBr2 and NiCl2, as alternatives to more expensive catalysts (e.g., bis(1,5-cyclooctadiene)nickel(0) (Ni(COD)2)). By catalyzing the polymerization of multi-block poly(phenylene) with NiBr2 and NiCl2, random copolymers with similar molecular weights could be prepared. However, these catalysts did not result in a high-molecular-weight polymer, limiting their wide scale application. Further, the amount of Ni(COD)2 could be reduced in this study by approximately 50% to synthesize poly(phenylene) multi-block copolymers, representing significant cost savings. Gel permeation chromatography and nuclear magnetic resonance results showed that the degree of polymerization and ion exchange capacity of the copolymers were almost the same as those achieved through conventional polymerization using 2.5 times as much Ni(COD)2. The flexible quaternized membrane showed higher chloride ion conductivity than commercial Fumatech membranes with comparable water uptake and promising chemical stability.

| S-EPMC7407201 | biostudies-literature

Functional Block Copolymers Carrying One Double-Stranded Ladderphane and One Single-Stranded Block in a Facile Metathesis Cyclopolymerization Procedure.

Project description:In order to improve the poor film-forming ability of polymeric ladderphane, di-block copolymers containing perylene diimide (PDI)-linked double-stranded poly(1,6-heptadiyne) ladderphane and branched alkyl side chains modified single-stranded poly(1,6-heptadiyne) were synthesized by metathesis cyclopolymerization (MCP) using Grubbs third-generation catalyst (Ru-III) in tetrahydrofuran solvent. The first block containing the ladderphane structure leads to higher thermal-stability, wider UV-vis absorption, lower LUMO level and ladderphane-induced rigidity and poor film-forming ability. The second block containing long alkyl chains is crucial for the guarantee of excellent film-forming ability. By comparing the effect of ladderphane structure on the resulted copolymers, single-stranded poly(1,6-heptadiyne) derivatives with PDI pedant were also processed. The structures of copolymers were proved by 1H NMR and gel permeation chromatography, electrochemical, photophysical, and thermal-stability performance were achieved by cyclic voltammetry (CV), UV-visible spectroscopy and thermogravimetric analysis (TGA) measurements. According to the experiment results, both copolymers possessed outstanding film-forming ability, which cannot be realized by small PDI molecules and oligomers. And they can serve as a superior candidate as for n-type materials, especially for their relatively wide range of light absorption (λ = 200~800 nm), and lower LUMO level (-4.3 and -4.0 eV).

| S-EPMC6829535 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data