scholarly journals Supramolecular Networks from Block Copolymers Based on Styrene and Isoprene Using Hydrogen Bonding Motifs—Part 1: Synthesis and Characterization

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1608 ◽  
Author(s):  
Elaine Rahmstorf ◽  
Volker Abetz
Keyword(s):  
Hydrogen Bonding ◽  
Block Copolymers ◽  
Ester Group ◽  
The Novel ◽  
Temperature Dependent ◽  
Scanning Calorimetry ◽  
Different Types ◽  
Supramolecular Networks ◽  
Subsequent Introduction ◽  
End Group

The combination of controlled anionic polymerization and subsequent introduction of hydrogen bonding groups was established to form thermo-reversible, supramolecular networks. Several polyisoprene-block-polystyrene-block-polyisoprene (ISI) copolymers—with polystyrene (PS) as the main block, and consequently giving the decisive material characteristics—were synthesized. The novel modification approach to post-functionalize the polyisoprene (PI) end-blocks and to introduce different motifs, which are able to form self-complementary hydrogen bonds, was attained. In the first step, hydroxylation was accomplished using 9-borabicyclo[3.3.1]nonane. Starting from the hydroxylated polymer, esterification with succinic anhydride was implemented to form an ester group with carboxylic end-group (-O-CO-CH2-CH2-COOH). In a second approach, 1,1’-carbonyldiimidazole was used as coupling agent to introduce various types of diamines (diethylenetriamine, triethylentetramine, and 2,6-diaminopyridine) to prepare urethane groups with amine end-group (-O-CO-NH-R-NH2). 1H NMR spectroscopy was used to confirm the successful synthesis and to calculate the degree of functionalization Df. Differential scanning calorimetry (DSC) showed a difference of the glass transition temperature Tg between unfunctionalized and functionalized block copolymers, but no greater influence between the different types of modification, and thus, on the Tg of the PS block. In temperature dependent FTIR spectroscopy, reversible processes were observed.

RAFT Polymerization of Monomers with Highly Disparate Reactivities: Use of a Single RAFT Agent and the Synthesis of Poly(styrene-block-vinyl acetate)

2013 ◽  
Vol 66 (12) ◽  
pp. 1564 ◽  
Author(s):  
Lily A. Dayter ◽  
Kate A. Murphy ◽  
Devon A. Shipp
Keyword(s):  
Block Copolymers ◽  
Vinyl Acetate ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Good Control ◽  
Scanning Calorimetry ◽  
Styrene Polymerization ◽  
Reversible Addition ◽  
Raft Agent ◽  
End Group

A single reversible addition–fragmentation chain transfer (RAFT) agent, malonate N,N-diphenyldithiocarbamate (MDP-DTC) is shown to successfully mediate the polymerization of several monomers with greatly differing reactivities in radical/RAFT polymerizations, including both vinyl acetate and styrene. The chain transfer constants (Ctr) for MDP-DTC for both these monomers were evaluated; these were found to be ~2.7 in styrene and ~26 in vinyl acetate, indicating moderate control over styrene polymerization and good control of vinyl acetate polymerization. In particular, the MDP-DTC RAFT agent allowed for the synthesis of block copolymers of these two monomers without the need for protonation/deprotonation switching, as has been previously developed with N-(4-pyridinyl)-N-methyldithiocarbamate RAFT agents, or other end-group transformations. The thermal properties of the block copolymers were studied using differential scanning calorimetry, and those with sufficiently high molecular weight and styrene composition appear to undergo phase separation. Thus, MDP-DTC may be useful for the production of other block copolymers consisting of monomers with highly dissimilar reactivities.

scholarly journals Preliminary assessment on cocrystals of nicotinamide:cinnamic acid and nicotinamide:p-coumaric acid at different solvents and ratio

2021 ◽  
Vol 15 (1) ◽  
pp. 101
Author(s):  
Mohamad Nor Amirul Azhar Kamis ◽  
Hamizah Mohd Zaki ◽  
Nornizar Anuar ◽  
Mohammad Noor Jalil Noor Jalil
Keyword(s):  
Hydrogen Bonding ◽  
Active Pharmaceutical Ingredient ◽  
Coumaric Acid ◽  
Hydrogen Bonding Interaction ◽  
Scanning Calorimetry ◽  
Molar Ratios ◽  
Bonding Interaction ◽  
Different Types ◽  
The Difference ◽  
Diffraction Patterns

Cocrystal plays an important role in the pharmaceutical industry to improve the low solubility and bioavailability of drugs. In this study, the cocrystal formation screening was carried out for nicotinamide(NIC) as the API (Active Pharmaceutical Ingredient) with two coformers; cinnamic acid (CIN), and p-coumaric acid (COU) using recrystallization method with different solvents (methanol, ethanol, and acetonitrile) and molar ratios of NIC:CIN and NIC:COU of 1:1, 1:2 and 2:1. The NIC:CIN and NIC:COU mixtures were characterized using Differential Scanning Calorimetry (DSC), Powder X-ray Diffraction (PXRD), and Fourier Transform Infrared (FTIR) to assess the formation of cocrystal. All characterization data for NIC:CIN mixtures showed that the use of different types of solvents and molar ratios have no significant effect on the formation of the cocrystal. The characterization data showed the formation of similar NIC:CIN cocrystal with no polymorphism with a melting temperature of 96–98 oC for all mixtures. The diffraction pattern of all NIC:CIN also showed similar new peaks at 2θ of 6.7°, 17.7°, 20.6°, 22.4°, and 25.1°. The DSC and PXRD data of NIC:CIN were supported by FTIR which revealed similar hydrogen bonding interaction for all NIC:CIN mixtures. The characterization of NIC:COU mixture revealed four different cocrystal forms with melting points of 118 °C, 152 °C, 160 °C, and 169 °C. The PXRD data of NIC:COU mixture also showed different diffraction patterns signifying distinct crystalline identities which supported with different FTIR spectrum validating the difference in hydrogen bonding interaction. It was observed that the use of different types of solvents did not give significant effects on the formation of NIC:CIN and NIC:COU cocrystals.   Keywords: Nicotinamide, Cocrystal Pre-Characterization, DSC, PXRD, FTIR

Molecular Networks Forming Crystalline and Liquid Crystalline Phases by Combined Hydrogen-Bonding and Ionic Interactions

2004 ◽  
Vol 69 (5) ◽  
pp. 1161-1168 ◽  
Author(s):  
Mir Wais Hosseini ◽  
Dimitris Tsiourvas ◽  
Jean-Marc Planeix ◽  
Zili Sideratou ◽  
Nicolas Thomas ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Liquid Crystalline ◽  
Molecular Networks ◽  
Ionic Interactions ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Alkyl Chains ◽  
Smectic Phases ◽  
Liquid Crystalline Phases ◽  
Supramolecular Networks

Molecular recognition of cyclic bisamidinium dication with a series of 4-alkoxybenzoates afforded materials exhibiting lamellar crystalline structures at low temperatures and highly ordered smectic phases at higher temperatures. The liquid crystalline behaviour was investigated by differential scanning calorimetry, polarized optical microscopy and established by X-ray diffraction. Combined hydrogen-bonding and ionic interactions resulted in supramolecular networks which have sufficient stability to maintain their structure at high temperatures following the melting of the long alkyl chains.

Thermally Responsive Elastomeric Supramolecular Polymers Featuring Flexible Aliphatic Hydrogen-Bonding End-Groups

2009 ◽  
Vol 62 (8) ◽  
pp. 790 ◽  
Author(s):  
Philip Woodward ◽  
Daniel Hermida Merino ◽  
Ian W. Hamley ◽  
Andrew T. Slark ◽  
Wayne Hayes
Keyword(s):  
Hydrogen Bonding ◽  
Network Formation ◽  
Supramolecular Network ◽  
Synthetic Approach ◽  
Temperature Dependent ◽  
Supramolecular Materials ◽  
Rheological Analysis ◽  
Thermally Responsive ◽  
End Groups ◽  
Supramolecular Networks

The present paper details the synthesis, characterization, and preliminary physical analyses of a series of polyisobutylene derivatives featuring urethane and urea end-groups that enable supramolecular network formation to occur via hydrogen bonding. These polymers are readily accessible from relatively inexpensive and commercially available starting materials using a simple two-step synthetic approach. In the bulk, these supramolecular networks were found to possess thermoreversible and elastomeric characteristics as determined by temperature-dependent rheological analysis. These thermoreversible and elastomeric properties make these supramolecular materials potentially very useful in applications such as adhesives and healable surface coatings.

Self-Assembly of Hydrogels From Elastin-Mimetic Block Copolymers

2002 ◽  
Vol 724 ◽  
Author(s):  
Elizabeth R. Wright ◽  
R. Andrew McMillan ◽  
Alan Cooper ◽  
Robert P. Apkarian ◽  
Vincent P. Conticello
Keyword(s):  
Block Copolymers ◽  
Self Assembly ◽  
Triblock Copolymers ◽  
Variable Temperature ◽  
Inverse Temperature ◽  
Temperature Transition ◽  
Scanning Calorimetry ◽  
Design Synthesis ◽  
Inverse Temperature Transition ◽  
Functional Biomaterials

AbstractTriblock copolymers have traditionally been synthesized with conventional organic components. However, triblock copolymers could be synthesized by the incorporation of two incompatible protein-based polymers. The polypeptides would differ in their hydrophobicity and confer unique physiochemical properties to the resultant materials. One protein-based polymer, based on a sequence of native elastin, that has been utilized in the synthesis of biomaterials is poly (Valine-Proline-Glycine-ValineGlycine) or poly(VPGVG) [1]. This polypeptide has been shown to have an inverse temperature transition that can be adjusted by non-conservative amino acid substitutions in the fourth position [2]. By combining polypeptide blocks with different inverse temperature transition values due to hydrophobicity differences, we expect to produce amphiphilic polypeptides capable of self-assembly into hydrogels. Our research examines the design, synthesis and characterization of elastin-mimetic block copolymers as functional biomaterials. The methods that are used for the characterization include variable temperature 1D and 2D High-Resolution-NMR, cryo-High Resolutions Scanning Electron Microscopy and Differential Scanning Calorimetry.

scholarly journals CRISPR-Cas System: The Powerful Modulator of Accessory Genomes in Prokaryotes

2021 ◽  
pp. 1-16
Author(s):  
Anca Butiuc-Keul ◽  
Anca Farkas ◽  
Rahela Carpa ◽  
Dumitrana Iordache
Keyword(s):  
Nucleic Acids ◽  
Pathogenic Bacteria ◽  
The Novel ◽  
Defense System ◽  
Guide Rnas ◽  
Crispr Array ◽  
Different Types ◽  
Evolutionary Trajectories ◽  
Novel Coronavirus ◽  
Cas Proteins

Being frequently exposed to foreign nucleic acids, bacteria and archaea have developed an ingenious adaptive defense system, called CRISPR-Cas. The system is composed of the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) array, together with CRISPR (<i>cas</i>)-associated genes. This system consists of a complex machinery that integrates fragments of foreign nucleic acids from viruses and mobile genetic elements (MGEs), into CRISPR arrays. The inserted segments (spacers) are transcribed and then used by cas proteins as guide RNAs for recognition and inactivation of the targets. Different types and families of CRISPR-Cas systems consist of distinct adaptation and effector modules with evolutionary trajectories, partially independent. The origin of the effector modules and the mechanism of spacer integration/deletion is far less clear. A review of the most recent data regarding the structure, ecology, and evolution of CRISPR-Cas systems and their role in the modulation of accessory genomes in prokaryotes is proposed in this article. The CRISPR-Cas system&apos;s impact on the physiology and ecology of prokaryotes, modulation of horizontal gene transfer events, is also discussed here. This system gained popularity after it was proposed as a tool for plant and animal embryo editing, in cancer therapy, as antimicrobial against pathogenic bacteria, and even for combating the novel coronavirus – SARS-CoV-2; thus, the newest and promising applications are reviewed as well.

scholarly journals Quadruple Hydrogen Bond-Containing A-AB-A Triblock Copolymers: Probing the Influence of Hydrogen Bonding in the Central Block

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4705
Author(s):  
Boer Liu ◽  
Xi Chen ◽  
Glenn A. Spiering ◽  
Robert B. Moore ◽  
Timothy E. Long
Keyword(s):  
Hydrogen Bonding ◽  
Self Assembly ◽  
Microphase Separation ◽  
Triblock Copolymers ◽  
Random Copolymer ◽  
Thermomechanical Properties ◽  
Structure Property ◽  
Scanning Calorimetry ◽  
Central Block ◽  
Quadruple Hydrogen Bonding

This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further confirming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths.

scholarly journals LCST polymers with UCST behavior

Soft Matter ◽  
2021 ◽  
Author(s):  
Marzieh Najafi ◽  
Mehdi Habibi ◽  
Remco Fokkink ◽  
Wim Hennink ◽  
Tina Vermonden
Keyword(s):  
Block Copolymers ◽  
Aqueous Solutions ◽  
Temperature Dependent ◽  
Dependent Behavior ◽  
Temperature Dependent Behavior

In this study, temperature dependent behavior of dense dispersions of core crosslinked flower-like micelles is investigated. Micelles were prepared by mixing aqueous solutions of two ABA block copolymers with PEG...

scholarly journals Thermodynamics and Intermolecular Interactions of Nicotinamide in Neat and Binary Solutions: Experimental Measurements and COSMO-RS Concentration Dependent Reactions Investigations

2021 ◽  
Vol 22 (14) ◽  
pp. 7365
Author(s):  
Piotr Cysewski ◽  
Maciej Przybyłek ◽  
Anna Kowalska ◽  
Natalia Tymorek
Keyword(s):  
Intermolecular Interactions ◽  
Vibrational Energy ◽  
Perfect Match ◽  
Zero Point ◽  
Heat Capacity Change ◽  
Free Energies ◽  
Temperature Dependent ◽  
Scanning Calorimetry ◽  
Capacity Change ◽  
Self Association

In this study, the temperature-dependent solubility of nicotinamide (niacin) was measured in six neat solvents and five aqueous-organic binary mixtures (methanol, 1,4-dioxane, acetonitrile, DMSO and DMF). It was discovered that the selected set of organic solvents offer all sorts of solvent effects, including co-solvent, synergistic, and anti-solvent features, enabling flexible tuning of niacin solubility. In addition, differential scanning calorimetry was used to characterize the fusion thermodynamics of nicotinamide. In particular, the heat capacity change upon melting was measured. The experimental data were interpreted by means of COSMO-RS-DARE (conductor-like screening model for realistic solvation–dimerization, aggregation, and reaction extension) for concentration dependent reactions. The solute–solute and solute–solvent intermolecular interactions were found to be significant in all of the studied systems, which was proven by the computed mutual affinity of the components at the saturated conditions. The values of the Gibbs free energies of pair formation were derived at an advanced level of theory (MP2), including corrections for electron correlation and zero point vibrational energy (ZPE). In all of the studied systems the self-association of nicotinamide was found to be a predominant intermolecular complex, irrespective of the temperature and composition of the binary system. The application of the COSMO-RS-DARE approach led to a perfect match between the computed and measured solubility data, by optimizing the parameter of intermolecular interactions.

Nucleobase-Containing Block Copolymers Having a High Interaction Parameter by Complementary Hydrogen Bonding

2021 ◽  
Author(s):  
Nari Shin ◽  
Seonghyeon Ahn ◽  
Eunsoel Kim ◽  
Eun Young Kim ◽  
So Yeong Park ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Block Copolymers ◽  
Interaction Parameter ◽  
High Interaction
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