Query: Side-Chain-Induced Rigid Backbone Organization of Polymer Semiconducto

Candidate papers:

abstract: While high mobility p type conjugated polymers have been widely reported, high mobility n type conjugated polymers are still rare. In the present work, we designed semifluorinated alkyl side chains and introduced them into naphthalene diimide based polymers (PNDIF T2 and PNDIF TVT) We found that the strong self organization of these side chains induced a high degree of order in the attached polymer backbones by forming a superstructure composed of "backbone crystals" and "side chain crystals" This phenomenon was shown to greatly enhance the ordering along the backbone direction, and the resulting polymers thus exhibited unipolar n channel transport in field effect transistors with remarkably high electron mobility values of up to 6.50 cm(2) V( 1) s( 1) and with a high on off current ratio of 10(5)
author_names: Boseok Kang

Ran Kim

Seon Baek Lee

Soon-Ki Kwon

Yun-Hi Kim

Kilwon Cho
title: Side Chain Induced Rigid Backbone Organization of Polymer Semiconductors through Semifluoroalkyl Side Chains.
venue: Journal of the American Chemical Society
year: 2016

abstract: Abstract The chain conformation of poly(2 vinylpyridine) (P2VP) complexed by 4 (4 (3,4,5 tris(dodecyloxy)benzoyl)oxy)phenyl)diazenyl)benzenesulfonic acid at different degrees of neutralization (DN) was addressed by small and wide angle neutron scattering technique. To get information on the conformation of P2VP chains spatially confined within lamellar and columnar mesophases at different DNs, the complexes were prepared from a blend of protonated and deuterated P2VP. The 2D scattering patterns of extruded fibers show that at low DN the complex self organizes in a lamellar phase. The inertial mean distances in the direction parallel and perpendicular to the fiber axis reveal the formation of compact disc like globules of individual P2VP chains at DN 25 and 33% With the increase of DN the interaction between the neighboring side groups along the backbone increases. This results in formation of hexagonal columnar phase at DN 50% in which the P2VP macromolecules are confined within cylindrical channels forming most probably a disordered helical conformation. At DN 1.0, the enhanced rigidity of the complex hinders the accommodation of the ligands at the interface with polymer chain. This results in appearance of non bonded side groups in the columns giving rise to a poorly ordered structure. In contrast to more rigid chains of poly(4 vinylpyridine) the transition from lamellar to columnar mesophase in P2VP occurs at lower DNs, indicating a significant role of the chain flexibility in the formation of ordered structures.
author_names: Denis V Anokhin

Kseniia N Grafskaia

Inessa A Izdelieva

Xiaomin Zhu

Dimitri A Ivanov
title: Polymer conformation in supramolecular complexes with wedge shaped ligands: Exploring the impact of the liquid crystalline organization
venue: Polymer
year: 2019

abstract: Comb like macromolecules 3 nnn consisting of poly(p phenylene vinylene)/poly(p phenylene ethynylene) polymer backbones bearing four flexible alkoxy substituents per constitutional unit are examined in their bulk states with respect to the length of the side chains attached on the phenylene ring located between the vinylene moities. Characterization of phase behaviour has been performed by means of polarized optical microscopy and differential scanning calorimetry. Structural ordering on the molecular size scale was deduced from a qualitative analysis of wide angle X ray scattering effects recorded for macroscopically oriented filaments using a two dimensional detector. Macromonomer 1 was also considered. All experimental results pointed out a highly ordered self organization of these materials with structure parameters depending on molecular details. For both macromonomer 1 and polymers 3 nnn, formation of supramolecular assemblies is detected as temperature dependent contributions of (1) spatial segregation between aromatic and aliphatic segments, (2) stacking properties of p conjugated fragments and (3) crystallization of the alkoxy side chains.
author_names: Benjamin Carbonnier

Tadeusz Pakula

Daniel Ayuk Mbi Egbe
title: Self organization of comb like macromolecules comprised of four fold alkoxy substituted (PPV PPE) rigid backbone repeat units: role of length variation of side chains attached on phenylene ring surrounded by vinylene moieties
year: 2005

abstract: Abstract 4 Hydroxy 4' cyanobiphenyl and 4 hydroxy 4' n pentylbiphenyl have been converted into vinyl monomers by reactions with acryloyl and methacryloyl chlorides. All four new monomers were homopolymerized free radically to yield acrylic polymers which melt with decomposition at temperatures in excess of 200degC. Powder X ray diffraction studies clearly show that the polymers are crystalline and suggest that the polymer backbones lie in essentially parallel planes contained within perpendicular smectic like layers of the directly attached and rigid anisotropic side chain substituents. It is noteworthy that side chain ordering is sufficiently strong to overcome the normal conformational barriers associated with main chain methyl groups in the methacrylate polymers. Previous examples of this type of ordering have been restricted to acrylate polymers.
author_names: A K Alimoglu

Anthony Ledwith

Peter Alan Gemmell

George William Gray

Dana Borden Lacy
title: Polymers with rigid anisotropic side groups: 1. Side chain induced crystallinity in substituted biphenyl acrylates and methacrylates
year: 1984

abstract: Abstract The synthesis, characterization and supramolecular organization of rigid flexible aromatic aliphatic polyethers are reported. The polymers contain substituted quinquephenyl moieties along their main chains separated by flexible aliphatic units of various lengths. The oligophenylene segments bear different types of dodecyloxy tailed side groups, either attached on the periphery of side dendritic wedges (G 1 or as direct side chains (G 0 Their structural characterization was performed by means of differential scanning calorimetry, polarizing optical microscopy and X ray scattering from oriented fibers. These techniques revealed the presence of supramolecular organization in different levels and in the absence of solvent, reflecting a delicate balance of interactions produced by the rigid flexible backbone segments and the size of dendritic side chains. It was concluded that the polymers with only two dodecyloxy side chains (zeroth generation, G 0 possess smectic order. On the other hand, substitution of the quinquephenyl backbone with the dodecyloxy decorated dendrons (first generation, G 1 disrupts the lateral order giving rise to a nematic state. These results are compared with the corresponding rigid flexible polyethers having terphenyl rigid segments.
author_names: P Riala

Aikaterini K Andreopoulou

Joannis K Kallitsis

Antonis Gitsas

George Floudas
title: Role of main chain rigidity and side chain substitution on the supramolecular organization of rigid flexible polymers
year: 2006

abstract: The glass transition temperature (Tg) of polymers is an important parameter that determines the kinetics of molecular organization of polymeric chains. Understanding the Tg of conjugated polymers i.
author_names: Anirudh Sharma

Xun Pan

Jonas Mattiasson Bjuggren

Desta Gedefaw

Xiaofeng Xu

Renee Kroon

Ergang Wang

Jonathan A Campbell

David A Lewis

Mats R Andersson
title: Probing the Relationship between Molecular Structures, Thermal Transitions, and Morphology in Polymer Semiconductors Using a Woven Glass Mesh Based DMTA Technique
venue: Chemistry of Materials
year: 2019

abstract: Abstract The relationship between the isotropization transition temperatures and the associated entropy changes of two series of side chain liquid crystalline polymers based on three different polymer backbones (polymethacrylate, polyacrylate and polymethylsiloxane) and 4 methoxy 4' hydroxy a methylstilbene and 4 hydroxy 4' methoxy a methylstilbene mesogenic side groups attached to the polymer backbone through different flexible spacers is discussed. In the case of polymers containing long flexible spacers, isotropization transition temperatures, which are mostly dictated by the side groups, are higher for polymers based on flexible backbones, suggesting that they provide the highest degree of order in the mesophase. Therefore, their mesophase should exhibit the lowest entropy and the highest entropy change of isotropization. However, experimentally determined entropy changes of isotropization, which refer to the overall degree of order of the polymer, present the highest values for polymers based on the most rigid backbone. Two different mechanisms of distortion of the random coil conformation of flexible and rigid polymer backbones are suggested to account for this contradictory result. A squeezed random coil conformation, which in the case of smectic polymers is confined between the smectic layers, is considered for flexible backbones. An extended chain conformation is considered for rigid backbones. The entropy associated with the squeezed random coil conformation is higher than that associated with the extended conformation, and therefore the overall order that results from the combination of backbone and the organization of the mesogenic side groups may explain the experimentally observed isotropization entropy changes. Polymers based on short flexible spacers exhibit similar entropy changes of isotropization irrespective of the nature of their backbone. This may suggest an extended backbone conformation for polymers based on short spacers and rigid or flexible backbones.
author_names: Virgil Percec

Dimitris Tomazos
title: Can the rigidity of a side chain liquid crystalline polymer backbone influence the mechanism of distortion of its random coil conformation?
year: 1990

abstract: Shape persistent macrocycles based on the phenylene ethynylene butadiynylene backbone with extraannular amino groups were synthesized by the oxidative dimerization of the corresponding (BOC protected) half ring bisacetylenes. ABA block structures with a central rigid macrocycle and a flexible periphery (oligoalkyl and oligostyryl groups) were subsequently obtained by carbodiimide directed coupling of the macrocyclic diamines with the corresponding carboxylic acids. Depending on the solvent, an aggregation of the compounds toward tubular supramolecular polymer brushes could be induced. Cryogenic transmission electron microscopy and small angle neutron scattering reveal the tubelike aggregates in solution. Atomic force microscopy confirms the morphology of these aggregates after casting onto surfaces. The aggregate growth occurs remarkably slowly. Solvophobic interactions good solubility of the flexible substituents and weak solubility of the rigid macrocycle combined with the oblate shape of the latter are.
author_names: Martina Fritzsche

Stefan-S Jester

Sigurd Hoger

Christina Klaus

Nico Dingenouts

Peter Linder

Markus Drechsler

Sabine Rosenfeldt
title: Self Organization of Coil Ring Coil Structures into Tubular Supramolecular Polymer Brushes: Synthesis, Morphology, and Growth
year: 2010

abstract: The ability to widely tune the design of macromolecular bottlebrushes provides access to self assembled nanostructures formed by microphase segregation in melt, thin film and solution that depart from structures adopted by simple linear copolymers. A series of random bottlebrush copolymers containing poly(3 hexylthiophene) (P3HT) and poly(d,l lactide) (PLA) side chains grafted on a poly(norbornene) backbone were synthesized via ring opening metathesis polymerization (ROMP) using the grafting through approach. P3HT side chains induce a physical aggregation of the bottlebrush copolymers upon solvent removal by vacuum drying, primarily driven by attractive p p interactions; however, the amount of aggregation can be controlled by adjusting side chain composition or by adding linear P3HT chains to the bottlebrush copolymers. Coarse grained molecular dynamics simulations reveal that linear P3HT chains preferentially associate with P3HT side chains of bottlebrush copolymers, which tends to reduce the aggregation. The nanoscale morphology of microphase segregated thin films created by casting P3HT PLA random bottlebrush copolymers is highly dependent on the composition of P3HT and PLA side chains, while domain spacing of nanostructures is mainly determined by the length of the side chains. The selective removal of PLA side chains under alkaline conditions generates nanoporous P3HT structures that can be tuned by manipulating molecular design of the bottlebrush scaffold, which is affected by molecular weight and grafting density of the side chains, and their sequence. The ability to exploit the unusual architecture of bottlebrushes to fabricate tunable nanoporous P3HT thin film structures may be a useful way to design templates for optoelectronic applications or membranes for separations.
author_names: Suk-Kyun Ahn

Jan Michael Carrillo

Jong K Keum

Jihua Chen

David M Uhrig

Bradley S Lokitz

Bobby G Sumpter

S Michael Kilbey
title: Nanoporous poly(3 hexylthiophene) thin film structures from self organization of a tunable molecular bottlebrush scaffold.
venue: Nanoscale
year: 2017

abstract: A series of methacrylate based side chain liquid crystal polymers have been prepared with a range of molecular weight. For the high molecular weight polymers, a smectic phase is observed with a very narrow nematic range. However at low molecular weight only the nematic phase is observed. A marked reduction in Tg, Tsn and Tnias a function of reducing the molecular weight have been observed. Infrared dichroism measurements have been made to determine the order parameters of the liquid crystalline side chain polymers. It is found that the higher the molecular weight of the polymer the higher is the threshold voltage of the electro optic response, and the lower the order parameter. The increase in the threshold voltage with increasing molecular weight may be related to the intrinsic curvature elasticity and hence to the coupling between mesogenic units and the polymer backbone. Introduction:The design principles of side chain liquid crystal polymers are well established [1] These molecular composites consist of a flexible polymer backbone and a rigid mesogenic unit, joined as a side chain to the polymer backbone by means of a flexible coupling chain .Although there were initial suggestions that the spacer chain would decouple the motion of the mesogenic unit from the polymer backbone it is now clear that the relatively short length of the coupling chains will result in some interaction between the mesogenic units and the polymer backbone chains. The theoretical predictions of Warner et al [2,3] and others [4] have been substantiated by a number of neutron scattering studies [5,10] In the nematic phase, the coupling in systems based upon methacrylates appears to be negative in the sense that the polymer chains lie preferentially perpendicular to the mesogenic units [5,10] in contrast to the parallel arrangement in a crylate based backbones [7] for the smectic phase, the density of the layered structure of the mesogenic units acts to confine the polymer chain to a layer perpendicular to the mesogenic units [5,6,8,10] although there is some possibility of interlayet hopping by the polymer chain [11] By suitable chemical design, polymers can be synthesized that will exhibit [12,13] The well known electric and magnetic filed effects displayed by low molar mass counterparts [14] In such electro optic effects, what is the role of the polymer backbone? It is clear that the polymetric nature of the liquid crystal phase strongly effects the response times through a highly temperature dependent viscosity. Furthermore the electro optic response of a side chain liquid crystal polymer is particularly sensitive to the thermal history of each sample, and this may be related to the coupling of the side chain organization to the very long relaxation time of the polymer backbone [15] In this contribution we focus on the role of the polymer backbone in determining the static properties of the liquid crystal phase. In particular we want to give attention on the influence of the molecular weight upon curvature elasticity, which determines the case with which the director pattern may be modified using external electric fields. We shall consider a dd`l 1 @ljm @ybrtl @ylk @yssl' lbb `mj a b 0229 m @yssl' @ybrtl @ylkl ynthl ywnsl yml`l rmtw'ml /Skh dd` 5 5 0222 m 433 series of methacrylate based side chain liquid crystal homopolymers in which the molecular weight is systematically varied. The state of orientational order in these homopolymers is evaluated through the use of infra red spectroscopy which selectively probes only the mesogenic side chains. Carefully programmed electro optic measurements are used to evaluate the relationships between the variation in molecular weight, orientational order and electro optical properties. Materials:A series of methacrylate based side chain liquid crystalline homopolymers of the repeat unit shown have been prepared by free radical polymerization [16] The standard conditions used, (initiation by AIBN in chlorobenzene at 55C) have been modified to give a range of molecular weight by increasing the initiator concentration and by the addition of various amounts of dodecanethiol [17] as a chain transfer agent [18] Both of these modifications reduce the molecular weight of the polymer produced. The homopolymers are characterized by a smectic phase, identified as sceectic A by Davideon et. al. [19] over the greater part of the liquid crystal range. A nematic phase is seen over a narrow temperature range close to the clearing point. On reducing the molecular weight all of the phase transitions, Tg TSN and TNI are depressed (table 1) as has been seen for polyacrylate and polysiloxane based side chain liquid crystalline polymer systems [20,21] At low molecular weights however, (polymer 4 and 5) the smectic to nematic transition is no longer observed by DSC and no textural features characteristic of smectic phases can be observed by polarizing microscopy. This itself is not conclusive proof of the absence of a smectic phase since those materials which do exhibit textures identifiable as smectic only do so when annealed well below the apparent S N transition (as determined by DSC) Annealing of polymer samples 4 and 5 at temperatures well below TNI did not yield textures characteristic of the smectic phase. dd`l 1 @ljm @ybrtl @ylk @yssl' lbb `mj a b 0229 m @yssl' @ybrtl @ylkl ynthl ywnsl yml`l rmtw'ml /Skh dd` 5 5 0222 m 434 Table 1 Molecular weight and Phase Transition Data 2 no phase transition observed When interpreting the phase behaviour of these materials we have to be cautious in attributing effects solely to differences in molecular weight: in the lowest molecular weight members of this series a significant percentage of end groups will be chain transfer agent fragments, consisting of a long alkyl chain bound through a sulphur atom. This percentage has been determined by micro analysis for the sulphur content of the polymers [16] and has been found to be 20% for 5 and 14% for 4 In order to ascertain whether the plasticizing effect of the dodecyl chains is responsible for the anomalous phase behaviour, we prepared a series of copolymers of the liquid crystalline monomer and dodecyl methacrylate, under conditions similar to that of polymer 2. These materials showed similar phase behaviour to the homopolymers, in terms of detectable smectic to nematic and nematic to isotropic phase transitions, even when up to 15 mol% of the non mesogenic monomer was incorporated. The molecular weight data were determined by G.P.C. (RAPRA Ltd) at room temperature in tetraphydrofuran, using a combination of concentration and viscosity detectors and UNICAL universal calibrattion software. Experimental Methods:An electro optic experiment involves the measurement of changes in the optical properties of thin films of the liquid crystal polymers induced through the application of electric fields. The experimental arrangment used for these electro optic measurements has been described previously in detail elsewhere [15,22) The electro optic cell (described below) was held inside a temperature controlled stage providing a uniform temperature environment with functions of 0.25C. the optical system w n g SN NI dd`l 1 @ljm @ybrtl @ylk @yssl' lbb `mj a b 0229 m @yssl' @ybrtl @ylkl ynthl ywnsl yml`l rmtw'ml /Skh dd` 5 5 0222 m 435 consisted on a 5mW helium neon laser with crossed polarizer and analyzer system and a photodiode with amplifier for intensity measurements. Electric fields were provided by means of a power amplifier (Hewlett packard 6827 A) driven by a function generator (Thandar TG 501) this arrangement provided waveforms in the frequency range 0.05 to 30 KHz with peak to peak voltages in the range 0 to 240 volts. The intensity of the transmitted light through this optical system was recorded as a function of time using a microcomputer system based around a IBM compatible PC. Through the use of a specially written software system EOCS, sophisticated electrooptical experiments could be performed on a continuous or cyclic basis, involving temperature control, data recording, field switching and analysis [15] the electro optic cells with predefined director orientation were constructed from patterned tin oxide coated glass slides. After cleaning in an ultrasonic bath and drying, the cell electrodes were coated with a thin layer of a polyimide precursor consisting of a 5% solution of Rodehftal 322 in dimethylformamide using a spin coater. These coated slides were heated and tabbed in a single direction with a cloth. A small portion of the selected polymer sample was carefully applied onto one of the treated glass electrodes, which was then heated above its cleaning point in order to allow the trapped air to escape. The second glass electrode was then mounted above the first electrode using 0.025 mm thickness Kapton sheet as spacers. The quality of the direction orientation was confirmed through examination with a polarizing microscope. Complete and uniform director alignment was obtained by holding the completed electro optic cell at a temperature 1C below the measured clearing point for 15 hours. This technique was successful in inducing a uniform director alignment in electro optic cells for all the materials used in this work, in all cases, the predefined director alignment was parallel to the electrode surface and to the direction of rubbing. Some cells showed small numbers of defects such as small loops when examined using the polarizing microscope, however these largely disappeared after holding the cells at elevated temperatures. The orientational order parameter "S" for each polymer sample at a variety of temperatures was measured using infra red dichrosim employing a perkin Elmer 580B spectrometer fitted with a wire grid polarizer and heating stage [22] the order parameter measurements were made using monodom
author_names: A Khalkaf

Khawaja Sabir Hassain

A Abbas
title: he Effect Of The Molecular Weight On The Static Electro Optic Properties Of Methacrylate Based Side Chain Liquid Polymers
year: 2013