Phase Transitions in Polymers Containing Long Self-Assembled CH2 Sequences in the Side Chain: A Positron Lifetime Study

2010 ◽  
Vol 666 ◽  
pp. 71-74 ◽  
Author(s):  
Yang Yu ◽  
Günter Dlubek ◽  
Reinhard Krause-Rehberg ◽  
Mario Beiner ◽  
Elke Hempel
Keyword(s):  
Self Assembly ◽  
Positron Lifetime ◽  
Side Chain ◽  
Strong Increase ◽  
Side Chains ◽  
Reverse Effect ◽  
Alkyl Methacrylate ◽  
Short Side ◽  
The Mean ◽  
Hexyl Methacrylate

Positron lifetime annihilation spectroscopy (PALS) was used to study the temperature- dependence of sub-nanometer size local free volumes in two atactic poly(n-octadecyl methacrylate)s (PODMA) with different molecular weight. These materials exhibit short range layered structure with a self-assembly and crystallization of side chains. From the ortho-positronium (o-Ps) lifetime the size of free volume holes and its distribution are calculated. At a temperature Tm=311 ± 5 K, the mean hole volume <vh> shows an abrupt and strong increase from 0.15 nm3 to 0.2 nm3, which comes from the melting of side-chains. The reverse effect, attributed to side chain crystallization, was observed during cooling the samples at slightly lower temperatures. The lifetime result of PODMA is compared with semifluorinated polyesters in which the side chain has an oxydecylperfluorodecyl structure (-O-(CH2)10-(CF2)9-CF3). Long chain polymers without side-chains such as polyethylene and short side-chain poly(n-alkyl methacrylate)s: poly(methyl methacrylate) (PMMA) and poly(n-hexyl methacrylate) (PHMA) are also compared with these polymers.

Study on Preparation and Dispersion Effect of Polycarboxylate Superplasticizer with Broken Dentiform Structure

2011 ◽  
Vol 250-253 ◽  
pp. 984-989 ◽  
Author(s):  
Zhi Yong Liu ◽  
Chong Cui ◽  
Li Li
Keyword(s):  
Carboxylic Acid ◽  
Chemical Structure ◽  
Side Chain ◽  
Side Chains ◽  
Test Results ◽  
Dispersion Effect ◽  
Anionic Polymer ◽  
Short Side ◽  
Carboxylic Acid Groups ◽  
Radical Polymerisation

Based on the analysis of the chemical structure of polycarboxylate-type SPs grafted PEO side chains, as well as sulfonic and carboxylic acid groups, a kind of polycarboxylate-based SPs grafted varied PEO side chains were synthesized by using radical polymerisation techniques.The relative dispersing effectiveness of the SPs was evaluated in cement paste and concrete by measuring paste flow and concrete slumps. The test results indicat that the copolymers with shorter PEO side chains (with 9 and 14 EO units) give lower initial dispersing power but higher time retention,with the prolonging of PEO side chains the higher initial dispersing effect and the lower time retention can be received. The excellent dispersing property and time retention of synthesized SPs for cementious systems can be achieved by grafted long side chain(with 45 EO units) integrated with short side chain(9 or 14 EO) at the backbone of anionic polymer.

Precise polyethylene derivatives bearing mesogenic side-chains: delicate self-assembly depending on graft density

2020 ◽  
Vol 11 (8) ◽  
pp. 1454-1461 ◽  
Author(s):  
Wen-Ying Chang ◽  
Dong Shi ◽  
Xu-Qiang Jiang ◽  
Jia-Di Jiang ◽  
Yang Zhao ◽  
...  
Keyword(s):  
Self Assembly ◽  
Spacing Effect ◽  
Spatial Arrangement ◽  
Side Chain ◽  
Side Chains ◽  
Local Coupling ◽  
Graft Density

Precise polyethylene derivatives bearing mesogenic side-chains demonstrate a sophisticated side-chain spacing effect on the local coupling and spatial arrangement of the backbone and side-chains.

Effects of side chains of oxatub[4]arene on its conformational interconversion, molecular recognition and macroscopic self-assembly

2017 ◽  
Vol 53 (93) ◽  
pp. 12572-12575 ◽  
Author(s):  
Liu-Pan Yang ◽  
Fei Jia ◽  
Fangfang Pan ◽  
Zhi-Sheng Pan ◽  
Kari Rissanen ◽  
...  
Keyword(s):  
Molecular Recognition ◽  
Chain Length ◽  
Self Assembly ◽  
Side Chain ◽  
Side Chains ◽  
Side Chain Length ◽  
Conformational Interconversion ◽  
Assembly Behavior

The side-chain length of oxatub[4]arenes was shown to affect its conformational interconversion, molecular recognition and macroscopic self-assembly behavior.

scholarly journals Effect of perfluorosulfonic acid side chains on oxygen permeation in hydrated ionomers of PEMFCs: Molecular dynamics simulation approach

2020 ◽  
Author(s):  
Sung Hyun Kwon ◽  
Haisu Kang ◽  
Young-Jun Sohn ◽  
Jinhee Lee ◽  
Sunbo Shim ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Water Content ◽  
Polymer Electrolyte Membrane ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Side Chain ◽  
Side Chains ◽  
Perfluorosulfonic Acid ◽  
Short Side ◽  
Water Contents

Abstract We prepared two types of perfluorosulfonic acid (PFSA) ionomers with Aquivion (short side chain) and Nafion (long side chain) on a Pt surface and varied their water contents (2.92 ≤ λ ≤ 13.83) to calculate the solubility and permeability of O2 in hydrated PFSA ionomers on a Pt surface using full atomistic molecular dynamics (MD) simulations. The solubility and permeability of O2 molecules in hydrated Nafion ionomers were greater than those of O2 molecules in hydrated Aquivion ionomers at the same water content, indicating that the permeation of O2 molecules in the ionomers is affected not only by the diffusion coefficient of O2 but also by the solubility of O2. Notably, O2 molecules are more densely distributed in regions where water and hydronium ions have a lower density in hydrated Pt/PFSA ionomers. Radial distribution function (RDF) analysis was performed to investigate where O2 molecules preferentially dissolve in PFSA ionomers on a Pt surface. The results showed that O2 molecules preferentially dissolved between hydrophilic and hydrophobic regions in a hydrated ionomer. The RDF analysis was performed to provide details of the O2 location in hydrated PFSA ionomers on a Pt surface to evaluate the influence of O2 solubility in ionomers with side chains of different lengths. The coordination number of C(center)–O(O2) and O(side chain)–O(O2) pairs in hydrated Nafion ionomers was higher than that of the same pairs in hydrated Aquivion ionomers with the same water content. Our investigation provides detailed information about the properties of O2 molecules in different PFSA ionomers on a Pt surface and with various water contents, potentially enabling the design of better-performing PFSA ionomers for use in polymer electrolyte membrane fuel cells.

Hierarchical superstructures of norbornene-based polymers depending on dendronized side-chains

2016 ◽  
Vol 7 (33) ◽  
pp. 5304-5311 ◽  
Author(s):  
Dae-Yoon Kim ◽  
Dong-Gue Kang ◽  
Suyong Shin ◽  
Tae-Lim Choi ◽  
Kwang-Un Jeong
Keyword(s):  
Self Assembly ◽  
Ring Opening ◽  
Main Chain ◽  
The Self ◽  
Side Chain ◽  
Side Chains ◽  
Ring Opening Metathesis Polymerization ◽  
Metathesis Polymerization ◽  
Main Chain Polymers

For understanding the self-assembly behaviours of norbornene-based main-chain polymers depending on side-chain pendants, a series of polynorbornenes containing the programmed dendrons is newly designed and successfully synthesized via ring opening metathesis polymerization.

Influence of side-chain interactions on the self-assembly of discotic tricarboxyamides: a crystallographic insight

RSC Advances ◽  
2015 ◽  
Vol 5 (40) ◽  
pp. 31845-31851 ◽  
Author(s):  
Arpita Paikar ◽  
Apurba Pramanik ◽  
Debasish Haldar
Keyword(s):  
Self Assembly ◽  
The Self ◽  
Side Chain ◽  
Side Chains ◽  
Fiber Network

Side chains interactions promote the self-assembly of discotic tricarboxyamides to form an entangled fiber network and thermo responsive gel.

scholarly journals Temperature-induced phase transitions for amino acids with linear side chains

2014 ◽  
Vol 70 (a1) ◽  
pp. C170-C170
Author(s):  
Carl Henrik Görbitz ◽  
Pavel Karen ◽  
Michal Dusek ◽  
Václav Petříček
Keyword(s):  
Amino Acids ◽  
Low Temperature ◽  
Side Chain ◽  
Side Chains ◽  
Ambient Conditions ◽  
Short Side ◽  
Space Groups ◽  
Cell Parameters ◽  
Commensurate Phase ◽  
Chain Conformations

Two polymorphs are known to exist under ambient conditions for a number of amino acids (three for glycine). While investigations at high pressure have revealed a number of additional polymorphs, temperature-induced changes are rare. Low-temperature structures with modified side-chain conformations were identified for L- and DL-cysteine. Furthermore, racemates with linear side chains, such as DL-methionine and the non-standard DL-aminobutyric acid (DL-Abu), DL-aminopentanoic acid (DL-norvaline, DL-Nva) and DL-aminohexanoic acid (DL-norleucine, DL-Nle), undergo major crystalline rearrangements on transitions between P21/c and C2/c space groups [1], some of them entropy driven (disordering). As for the corresponding enantio-pure amino acids, we recently described related P21 and I2 structures at 105 K for L-Abu, both with Z' = 4 [2]. A short side-chain C–C bond (1.426 Å) in the only available CSD entry for L-Nle (at 298 K) [3] lead us to suspect that disorder could have been overlooked in the original refinement. L-Nva has not been described previously. We now present single-crystal X-ray determinations between 105 and 405 K for L-Abu, L-Nva and L-Nle, showing phase behavior of unprecedented complexity. For L-Abu and L-Nva we find three different forms in this temperature interval, while four different phases were found for L-Nle. Its known C2 structure with Z' = 1 prevails between 200 and 390 K, and the side chain is indeed disordered 2:1 over two positions. Above 390 K disorder is extensive; the space group remains C2 but cell parameters change. Upon cooling new low-temperature forms are observed at 200 and 170 K. Both are modulated, but to a different extent: data collected at 100 K reveal an almost commensurate phase, while the 180 K phase is fully incommensurate. This is, to our knowledge, the first observation of modulated structures for an amino acid, and also the first observations of major crystalline rearrangements akin to those seen for the corresponding racemates.

scholarly journals Thermoresponsive Molecular Brushes with a Rigid-Chain Aromatic Polyester Backbone and Poly-2-alkyl-2-oxazoline Side Chains

2021 ◽  
Vol 22 (22) ◽  
pp. 12265
Author(s):  
Elena Tarabukina ◽  
Emil Fatullaev ◽  
Anna Krasova ◽  
Maria Sokolova ◽  
Mikhail Kurlykin ◽  
...  
Keyword(s):  
Graft Copolymer ◽  
Cationic Polymerization ◽  
Main Chain ◽  
Side Chain ◽  
Side Chains ◽  
Short Side ◽  
Molecular Brushes ◽  
Rigid Chain ◽  
Aromatic Polyester ◽  
Linear Poly

A new polycondensation aromatic rigid-chain polyester macroinitiator was synthesized and used to graft linear poly-2-ethyl-2-oxazoline as well as poly-2-isopropyl-2-oxazoline by cationic polymerization. The prepared copolymers and the macroinitiator were characterized by NMR, GPC, AFM, turbidimetry, static, and dynamic light scattering. The molar masses of the polyester main chain and the grafted copolymers with poly-2-ethyl-2-oxazoline and poly-2-isopropyl-2-oxazoline side chains were 26,500, 208,000, and 67,900, respectively. The molar masses of the side chains of poly-2-ethyl-2-oxazoline and poly-2-isopropyl-2-oxazoline and their grafting densities were 7400 and 3400 and 0.53 and 0.27, respectively. In chloroform, the copolymers conformation can be considered as a cylinder wormlike chain, the diameter of which depends on the side chain length. In water at low temperatures, the macromolecules of the poly-2-ethyl-2-oxazoline copolymer assume a wormlike conformation because their backbones are well shielded by side chains, whereas the copolymer with short side chains and low grafting density strongly aggregates, which was visualized by AFM. The phase separation temperatures of the copolymers were lower than those of linear analogs of the side chains and decreased with the concentration for both samples. The LCST were estimated to be around 45 °C for the poly-2-ethyl-2-oxazoline graft copolymer, and below 20 °C for the poly-2-isopropyl-2-oxazoline graft copolymer.

Side chain position, length and odd/even effects on the 2D self-assembly of mono-substituted anthraquinone derivatives at the liquid/solid interface

RSC Advances ◽  
2015 ◽  
Vol 5 (113) ◽  
pp. 93337-93346 ◽  
Author(s):  
Yi Hu ◽  
Kai Miao ◽  
Bao Zha ◽  
Xinrui Miao ◽  
Li Xu ◽  
...  
Keyword(s):  
Self Assembly ◽  
Side Chain ◽  
Side Chains ◽  
Solid Interface ◽  
Anthraquinone Derivatives ◽  
Self Assembled

This work provides efficient methods for regulating self-assembled structures by changing the position, length and odd/even properties of the side chains.

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