scholarly journals Temperature dependant structural changes in thin films of random semifluorinated PMMA copolymers

2013 ◽  
Vol 28 (S2) ◽  
pp. S144-S160 ◽  
Author(s):  
Dieter Jehnichen ◽  
Peter Friedel ◽  
Romy Selinger ◽  
Andreas Korwitz ◽  
Martin Wengenmayr ◽  
...  
Keyword(s):  
Thin Films ◽  
Phase Separation ◽  
Structural Changes ◽  
Bulk Material ◽  
Fluorine Content ◽  
Film Surface ◽  
Phase Behaviour ◽  
Side Chain ◽  
Side Chains ◽  
Polymer Backbone

Semifluorinated (SF) side chain polymers show phase separation between polymer backbone and SF side chains. Due to strong interaction between SF segments the side chains determine the structure behaviour strongly, often resulting in layered structures in which backbones and layers of SF side chains alternate. The interest in this work was directed to find out the dependence of these structures on concentration of SF side chains. Thin films of random copolymers consisting of methylmethacrylate (MMA) and semifluorinated side chain methacrylate (SFMA) segments and with different fluorine content in the perfluoroalkyl side chains (abbreviated as H10F10 and H2F8) were prepared by spin-coating. Phase separation and structure changes were initiated by external subsequent annealing. Corresponding bulk material served as basic information. Generation of ordered structures and variation of film parameters were observed using different X-ray scattering methods (XRR, GIWAXS, and GISAXS). The phase behaviour in bulk is governed by the SF side chain amount and their specific fluorine content which control the self-organization tendency of SF side chains. Additionally, the confinement in thin films generates an orientation of side chains normally to film surface.

scholarly journals Structure-Activity Relationships of Sandalwood Odorants: Synthesis of a New Campholene Derivative

2010 ◽  
Vol 5 (9) ◽  
pp. 1934578X1000500
Author(s):  
Iris Stappen ◽  
Joris Höfinghoff ◽  
Gerhard Buchbauer ◽  
Peter Wolschann
Keyword(s):  
Structural Changes ◽  
Great Influence ◽  
Complete Loss ◽  
Side Chain ◽  
Side Chains ◽  
Quaternary Carbon ◽  
Structural Modifications ◽  
Structure Activity ◽  
Highly Sensitive ◽  
Sandalwood Odorants

Structural modifications of natural (-)-( Z)-β-santalol have shown that the sandalwood odor impression is highly sensitive, even to small structural changes. Particularly, the substitution of the quaternary carbon is of great influence on the scent. Epi-compounds with side chains in the endo-position possess sandalwood odor in only a few derivatives, whereas modifications at this side chain, as well as modification at the bicyclic ring systems mostly lead to a complete loss of sandalwood fragrance.

Effects of heme modification on oxygen affinity and cooperativity of human adult hemoglobin

2015 ◽  
Vol 19 (01-03) ◽  
pp. 301-307 ◽  
Author(s):  
Tomokazu Shibata ◽  
Eisuke Furuichi ◽  
Kiyohiro Imai ◽  
Akihiro Suzuki ◽  
Yasuhiko Yamamoto
Keyword(s):  
Structural Changes ◽  
Oxygen Affinity ◽  
Side Chain ◽  
Side Chains ◽  
Human Adult ◽  
Alkaline Transition ◽  
Functional Control ◽  
Adult Hemoglobin ◽  
The Relationship ◽  
Heme Cofactor

We substituted strongly electron-withdrawing trifluoromethyl ( CF 3) group(s) as heme side chain(s) of human adult hemoglobin (Hb) to achieve large alterations of the heme electronic structure, in order to elucidate the relationship between the oxygen ( O 2) binding properties of Hb and the electronic properties of heme peripheral side chains. The obtained results were compared with those of similar studies performed on myoglobin (Mb), e.g. (Nishimura R, Matsumoto D, Shibata T, Yanagisawa S, Ogura T, Tai H, Matsuo T, Hirota S, Neya S, Suzuki A, and Yamamoto Y. Inorg. Chem. 2014; 53: 9156–9165). These two proteins shared the common feature of a decrease in O 2 affinity upon the CF 3 substitution(s). Using the P50 value, which is the partial pressure of O 2 required for 50% oxygenation of a protein, and the equilibrium constant ( p K a ) of the "acid-alkaline transition" in the met form of a protein as measures of the O 2 affinity and the electron density of heme Fe atom of the protein, respectively, a linear p K a - log (1/P50) relationship was demonstrated for the Hb and Mb systems. The native Hb, however, deviated from the p K a - log (1/P50) relationship, while the native Mb followed it. These results highlighted the significance of the vinyl side chains of the heme cofactor in the functional control of Hb through tertiary and quaternary structural changes upon the oxygenation of the protein.

scholarly journals Variation of the Side Chain Branch Position Leads to Vastly Improved Molecular Weight and OPV Performance in 4,8-dialkoxybenzo[1,2-b:4,5-b′]dithiophene/2,1,3-benzothiadiazole Copolymers

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Robert C. Coffin ◽  
Christopher M. MacNeill ◽  
Eric D. Peterson ◽  
Jeremy W. Ward ◽  
Jack W. Owen ◽  
...  
Keyword(s):  
Thin Film ◽  
Molecular Weight ◽  
Thin Film Transistor ◽  
Power Conversion ◽  
Hole Mobility ◽  
Side Chain ◽  
Side Chains ◽  
Absorption Profile ◽  
Polymer Backbone ◽  
Chain Branch

Through manipulation of the solubilizing side chains, we were able to dramatically improve the molecular weight(Mw)of 4,8-dialkoxybenzo[1,2-b:4,5-b′]dithiophene (BDT)/2,1,3-benzothiadiazole (BT) copolymers. When dodecyl side chains (P1) are employed at the 4- and 8-positions of the BDT unit, we obtain a chloroform-soluble copolymer fraction withMwof 6.3 kg/mol. Surprisingly, by moving to the commonly employed 2-ethylhexyl branch (P2),Mwdecreases to 3.4 kg/mol. This is despite numerous reports that this side chain increases solubility andMw. By moving the ethyl branch in one position relative to the polymer backbone (1-ethylhexyl,P3),Mwis dramatically increased to 68.8 kg/mol. As a result of thisMwincrease, the shape of the absorption profile is dramatically altered, withλmax= 637 nm compared with 598 nm forP1and 579 nm forP2. The hole mobility as determined by thin film transistor (TFT) measurements is improved from~1×10−6 cm2/Vs forP1andP2to7×10−4 cm2/Vs forP3, while solar cell power conversion efficiency in increased to2.91%forP3relative to0.31%and0.19%forP1andP2, respectively.

scholarly journals Surface Segregation of Amphiphilic PDMS-Based Films Containing Terpolymers with Siloxane, Fluorinated and Ethoxylated Side Chains

Coatings ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 153 ◽  
Author(s):  
Elisa Martinelli ◽  
Elisa Guazzelli ◽  
Antonella Glisenti ◽  
Giancarlo Galli
Keyword(s):  
Photoelectron Spectroscopy ◽  
Surface Segregation ◽  
Water Environment ◽  
Film Surface ◽  
Side Chain ◽  
Chemical Compositions ◽  
Side Chains ◽  
Air Interface ◽  
High Enrichment ◽  
Surface Active

(Meth)acrylic terpolymers carrying siloxane (Si), fluoroalkyl (F) and ethoxylated (EG) side chains were synthesized with comparable molar compositions and different lengths of the Si and EG side chains, while the length of the fluorinated side chain was kept constant. Such terpolymers were used as surface-active modifiers of polydimethylsiloxane (PDMS)-based films with a loading of 4 wt%. The surface chemical compositions of both the films and the pristine terpolymers were determined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS) at different photoemission angles. The terpolymer was effectively segregated to the polymer−air interface of the films independent of the length of the constituent side chains. However, the specific details of the film surface modification depended upon the chemical structure of the terpolymer itself. The exceptionally high enrichment in F chains at the surface caused the accumulation of EG chains at the surface as well. The response of the films to the water environment was also proven to strictly depend on the type of terpolymer contained. While terpolymers with shorter EG chains appeared not to be affected by immersion in water for seven days, those containing longer EG chains underwent a massive surface reconstruction.

scholarly journals Crystallization of dienelactone hydrolase in two space groups: structural changes caused by crystal packing

2014 ◽  
Vol 70 (7) ◽  
pp. 884-889 ◽  
Author(s):  
Joanne L. Porter ◽  
Paul D. Carr ◽  
Charles A. Collyer ◽  
David L. Ollis
Keyword(s):  
Structural Changes ◽  
Crystal Packing ◽  
Side Chain ◽  
Side Chains ◽  
Citrate Buffer ◽  
Space Group ◽  
Space Groups ◽  
Crystal Contacts ◽  
Dienelactone Hydrolase ◽  
Substrate Inhibitor

Dienelactone hydrolase (DLH) is a monomeric protein with a simple α/β-hydrolase fold structure. It readily crystallizes in space groupP212121from either a phosphate or ammonium sulfate precipitation buffer. Here, the structure of DLH at 1.85 Å resolution crystallized in space groupC2 with two molecules in the asymmetric unit is reported. When crystallized in space groupP212121DLH has either phosphates or sulfates bound to the protein in crucial locations, one of which is located in the active site, preventing substrate/inhibitor binding. Another is located on the surface of the enzyme coordinated by side chains from two different molecules. Crystallization in space groupC2 from a sodium citrate buffer results in new crystallographic protein–protein interfaces. The protein backbone is highly similar, but new crystal contacts cause changes in side-chain orientations and in loop positioning. In regions not involved in crystal contacts, there is little change in backbone or side-chain configuration. The flexibility of surface loops and the adaptability of side chains are important factors enabling DLH to adapt and form different crystal lattices.

Liquid crystalline polymers

2004 ◽  
Author(s):  
Sangdil I. Patel ◽  
Fred J. Davis
Keyword(s):  
Liquid Crystalline ◽  
Main Chain ◽  
Liquid Crystalline Polymers ◽  
Phase Behaviour ◽  
Side Chain ◽  
Polymer Backbone ◽  
Crystalline Materials ◽  
Crystalline Polymers ◽  
Anisotropic Behaviour ◽  
Liquid Crystalline Materials

The idea of combining the anisotropic behaviour of liquid crystalline materials with the properties of macromolecular systems was first suggested by Onsanger and subsequently Flory. The actual realization that such systems could exist came from studies of natural polymers such as the tobacco mosaic virus. Interest in these systems intensified with the development of highstrength systems, based on rigid-rod systems, notably the aramid fibres, however, liquid crystallinity in such systems occurs only at high temperatures, usually close to the decomposition point of the polymer. It was only in the late 1970s that the design criteria for liquid crystalline polymers became apparent, the secret being largely in the decoupling of the rigid aromatic groups which give rise to the anisotropic behaviour. As a result of these ideas two classifications of liquid crystalline materials were described. Main-chain liquid crystalline polymers, are those in which rigid aromatic molecules form part of the polymer backbone, either as a continuous chain or separated by a series of methylene groups in order to lower temperature at which liquid crystalline phase behaviour is observed. Side-chain systems resemble the comb-like systems studied by Shibaev and Plate, and have the rigid aromatic groups attached as a side-chain. In general, the monomer systems required for main-chain liquid crystalline polymers are relatively simple; synthetically these systems are prepared by step-growth methods and the main challenge is often maintaining sufficient solubility to allow suitable chain-lengths to be grown (an example of how such problems might be overcome is given in Chapter 4). Side-chain systems tend to be produced from more complex structural sub-units, and may be produced either by polymerization of the appropriate monomer or by functionalization of a preformed polymer backbone. Examples of both approaches are given in this chapter. From a practical viewpoint, the advantage of side-chain systems is that they tend to be much more soluble in common organic solvents and also that thermal phase transitions occur at reasonable temperatures (reasonable being well below the temperature at which the polymer decomposes). A further advantage of such side-chain systems is that the phase behaviour can be effectively tuned through the chemical modifications of the three components, namely the side-group, the flexible coupling chain and the polymer backbone.

scholarly journals Side-chain tuning in conjugated polymer photocatalysts for improved hydrogen production from water

2020 ◽  
Vol 13 (6) ◽  
pp. 1843-1855 ◽  
Author(s):  
Duncan J. Woods ◽  
Sam A. J. Hillman ◽  
Drew Pearce ◽  
Liam Wilbraham ◽  
Lucas Q. Flagg ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Conjugated Polymer ◽  
Chemical Structure ◽  
Side Chain ◽  
Side Chains ◽  
Structure Property ◽  
Polymer Backbone ◽  
Solution Processable

Structure–property–activity relationships in solution processable polymer photocatalysts for hydrogen production from water were probed by varying the chemical structure of both the polymer side-chains and the polymer backbone.

scholarly journals Use of side-chain for rational design of n-type diketopyrrolopyrrole-based conjugated polymers: what did we find out?

2014 ◽  
Vol 16 (32) ◽  
pp. 17253-17265 ◽  
Author(s):  
Catherine Kanimozhi ◽  
Nir Yaacobi-Gross ◽  
Edmund K. Burnett ◽  
Alejandro L. Briseno ◽  
Thomas D. Anthopoulos ◽  
...  
Keyword(s):  
Conjugated Polymers ◽  
Intermolecular Interactions ◽  
Electron Mobility ◽  
Rational Design ◽  
Side Chain ◽  
Side Chains ◽  
Polymer Backbone ◽  
Alternating Copolymers

Electron mobility of diketopyrrolopyrrole (DPP) based alternating copolymers of >2 cm2V−1s−1requires the combination of strong intramolecular conjugation along the polymer backbone with optimized intermolecular interactions that can be tuned with suitable side-chains.

Vapor Treatment of Block Copolymer Thin Films: GISAXS and Simulations

2014 ◽  
Vol 70 (a1) ◽  
pp. C877-C877
Author(s):  
Jianqi Zhang ◽  
Dorthe Posselt ◽  
Alessandro Sepe ◽  
Jan Perlich ◽  
Detlef-M. Smilgies ◽  
...  
Keyword(s):  
Thin Films ◽  
Computer Simulations ◽  
Structural Changes ◽  
Structural Evolution ◽  
Film Surface ◽  
Grazing Incidence ◽  
Solvent Uptake ◽  
The Times ◽  
Chain Conformations ◽  
Vapor Treatment

The structural evolution in poly(styrene-b-butadiene) (P(S-b-B)) diblock copolymer thin films during treatment with cyclohexane vapor is investigated in-situ and in real-time using grazing-incidence small-angle X-ray scattering (GISAXS) [1]. Both the swelling and the drying process are investigated. The lamellae are initially perpendicular to the film surface, i.e. the film is laterally nanostructured. Cyclohexane is a good solvent for PB and a theta solvent for PS, i.e., it is slightly selective. Using incident angles above and below the polymer critical angle, structural changes near the film surface and in the entire film are distinguished. We find that, during swelling, the initially perpendicular lamellae tilt within the film. Our computer simulations [2] show that this is due to the tendency of the copolymers to assume less stretched chain conformations, i.e. the lamellae shrink upon solvent uptake. Since long-range mass transport is not easily possible, tilting allows satisfying the space-filling condition when the lamellae are shrinking. Surface-sensitive GISAXS experiments show that, at the film surface, the lamellae eventually vanish at the expense of a thin PB wetting layer. During the subsequent drying, the perpendicular lamellae reappear at the surface, and finally, PS blocks protrude because of the solvent selectivity. By modeling the 2D GISAXS images, the time-dependent height of the protrusions can be quantitatively extracted. Figure 1. (a) 2D GISAXS images during swelling (top row) and drying (bottom row). The times after the beginning of the vapor treatment are indicated. (b) Snapshots from computer simulations of perpendicular lamellae which tilt during the film swelling. From left to right, the degree of swelling increases.

Rational design of conjugated side chains for high-performance all-polymer solar cells

2018 ◽  
Vol 3 (1) ◽  
pp. 103-112 ◽  
Author(s):  
Wei Huang ◽  
Meilin Li ◽  
Fengyuan Lin ◽  
Yang Wu ◽  
Zhifan Ke ◽  
...  
Keyword(s):  
Solar Cells ◽  
Phase Separation ◽  
High Performance ◽  
Rational Design ◽  
Polymer Solar Cells ◽  
Energy Levels ◽  
Fine Tuning ◽  
Side Chain ◽  
Side Chains

High-performance all-polymer solar cells were developed by employing an asymmetric benzo[1,2-b:4,5-b′]dithiophene unit with one thiophene and one 4-methoxythiophene conjugated side chain in the donor polymer, which enabled fine-tuning of energy levels and phase separation.

Sign in / Sign up

Export Citation Format

Share Document