Synthesis and characterization of bulky side chain methacrylate polymers

The synthesis, and dilute solution behavior of poly(2,4-dimethylphenyl methacrylate) (2,4DMP), poly(2,5-dimethylphenyl methacrylate) (2,5DMP), and poly(3,5-dimethylphenyl methacrylate) (3,5DMP) is described. Comparison is made with results reported for other bulky side chain polymers. The Kuhn-Mark-Houwink-Sakurada (KMHS) relationships were established. The unperturbed dimensions 〈r²〉 ${}_{\text{½}}^{\text{0}}$ , the rigidity factor σ, the characteristic ratio C_∞, and the thermodynamic parameters were determined, using the Stockmayer-Fixman equation, from viscometric data in good solvents. The high rigidity observed for these polymers is explained assuming that these polymers behave as kinked-chains.     

Effects of thiophene units on substituted benzothiadiazole and benzodithiophene copolymers for photovoltaic applications

Two conjugated copolymers, poly{4,7-[5,6-bis(octyloxy)]benzo(c)(1,2,5)thiadiazole-alt-4,8-di(2-ethylhexyloxyl)benzo[1,2-b:3,4-b]dithiophene} ( P1 ) and poly(2-{5-[5,6-bis(octyloxy)-4-(thiophen-2-yl)benzo(c)(1,2,5)thiadiazol-7-yl] thiophen-2-yl}-4,8-di(2-ethylhexyloxyl)benzo(1,2-b:3,4-b)dithiophene) ( P2 ), composed of benzodithiophene and 5,6-dioctyloxybenzothiadiazole derivatives with or without thiophene units were synthesized via a Stille cross-coupling polymerization reaction. These copolymers are promising for applications in bulk heterojunction solar cells because of their good solubility, proper thermal stability, moderate hole mobility, and low band gap. The photovoltaic properties of these copolymers were investigated on the basis of blends of the different polymer/(6,6)-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) weight ratios under AM1.5G illumination at 100 mW/cm². The device with indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/ P2: PC₇₁BM (1 : 2 w/w)/Ca/Al gave a relatively better photovoltaic performance with a power conversion efficiency of 1.55%. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Chiral liquid crystalline side chain polymers

Summary Optically active liquid crystalline side chain polymers with dif ferent flexible spacer groups (n=2–11) and different main chains (acry lates, methacrylates and α chloroacrylates) are described. (+)-2-methyl butyloxyphenyl esters of benzoic acid were chosen as the mesogenic group.     

Viscoelastic properties of (cellulose oligo-oxymethylene ether) acylates with bulky side chain

A series of (cellulose oligo-oxymethylene ether) acylates (COAs) are characterized by the presence of the micro-Brownian motion of the side chain (β process) which appears separately from that of the main chain (α process). Both the alpha; and β processes are largely affected by the kind of acyl groups introduced in the side chain. To clarify the effect of the acyl group on these processes, we investigated the dynamic mechanical properties of newly prepared COAs with acyl side chain, bulky in chemical structure (iso-butyrate, privalate, and benzoate) in relation to those for COAs with linear acyl side chain (acetate, butyrate, and valerate). By substituting bulky acyl isomer for linear acyl group in COAs, we observed that the temperature region of both the α and β processes moved to higher temperature. Furthermore, with an increase in molecular size of bulky acyl group, the β region shifts were much larger than the α region, indicating that the mobility of the side chain became comparable to that of the main chain. Finally, when such a large bulky group, for example, benzoate was introduced, the micro-Brownian motion of the side chain prior to that of the main chain ceased. The apparent activation energy for a third process (γ) due to the motion of the oligo-oxymethylene parts in the side chain was estimated to be 10.3 kcal/mol.     

Synthesis and characterization of new side chain liquid crystalline polymers based on poly(dipropargylamine) main chain

Summary A new thermotropic side-chain liquid crystalline polymers based on poly (dipropargylamine) backbone were prepared by metathesis polymerization with transition metal catalysts. It was found that the MoCl₅-EtAlCl₂ catalyst system were very effective for the cyclopolymerization of presently investigated monomers. Resulting polymers were soluble in common organic solvents such as THF, chloroform, etc. The number-average molecular weight ( ) values of the polymers were in the range of 6.49x10³–11.6x10³, relative to polystyrene standard by GPC. Thermal properties of the monomers and the polymers synthesized were examined by differential scanning calorimetry (DSC) and cross-polarized optical microscopy. Both monomer and polymer displayed enantiotropic liquid crystallinity showing the reversible phase transition.     

Conjugated polymers based on benzodithiophene and arylene imides: Extended absorptions and tunable electrochemical properties

Three novel conjugated polymers have been designed and synthesized via the alternative copolymerization of the electron-donating monomer benzodithiophene (BDT) and three different electron-accepting monomers: perylene diimide (PDI), naphthalene diimide (NDI), and phthalimide (PhI). All obtained copolymers show good solubility in common organic solvents as well as broader absorptions in visible region and narrower optical band gaps compared to homopolymers from BDT units. It is found that the absorptions of the copolymers are red-shifted with increasing the electron-withdrawing ability of the co-monomer. In particular, the absorption edge of P(BDT-NDI) film extends to 760 nm, whereas that of P(BDT-PhI) film is only at 577 nm. Cyclic voltammograms of the three polymers disclose that P(BDT-PDI) and P(BDT-NDI) are typical n-type materials because PDI and NDI are strong electron-accepting groups, while P(BDT-PhI) is a stable p-type material where the weak electron-withdrawing monomer (PhI) is introduced. The results suggest that the absorption range and the electrochemical properties of the conjugated polymers can be tuned by appropriate molecule-tailoring, which will help exploring ideal conducting polymers for potential applications in polymer optoelectronics, especially in polymer solar cells.     

Ring opening reactions of glycidyl methacrylate copolymers to introduce bulky organosilicon side chain substituents

Summary Glycidyl methacrylate (GMA) random copolymers with methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (BA), methyl methacrylate (MMA), ethyl methacrylate (EMA) and n-butyl methacrylate (BMA) were synthesized by solution free radical polymerizations, at 70±1 °C using α,α’-azobis(isobutyronitrile) as an initiator to give the copolymers I – VI in good yields. The copolymer compositions were obtained using related ¹H NMR spectra and the polydispersity indices of the copolymers determined using gel permeation chromatography (GPC). Tris(trimethylsilyl)methyl (Tsi=trisyl) groups were then covalently attached to the obtained copolymers as side chains by ring opening reaction between excess of TsiLi and expoxide groups of GMA units to give the copolymers I_Tsi – VI_Tsi in good yields. In the coupling reaction, the TsiLi reacted selectively with the epoxy groups of the backbone polymer rather than with the carbonyl groups of the backbone. This method of preparing functionalized silanes is limited by the readiness with which TsiLi abstracts a proton, if one is available, rather than attacks at carbon. In addition in the reaction with epoxides, the product alkoxide can transfer a silyl group from carbon to oxygen or ring opening polymerization. However these were shown not to occur at the conditions of interest here. The epoxy group possesses a higher reactivity for the TsiLi than the ester and chloromethyl groups. The ring opening reaction between the epoxy group and the TsiLi is simple and fast. All the resulted polymers were characterized by FT-IR and ¹H NMR spectroscopic techniques. The glass transition temperature (Tg) of all copolymers was determined by differential scanning calorimetry (DSC) apparatus. All the polymers containing trisyl groups showed a high glass transition temperature in comparison with unmodified copolymers (I – VI). Attaching the tris(trimethylsilyl)methyl group to macromolecular chain should lead to important modifications of polymer properties such as gas permeability and perm selectivity parameters.     

Laser irradiation of oligosiloxane copolymer thin films functionalized with side chain bulky carbosilane moieties

Linear oligosiloxanes functionalized with bulky side chain tris(trimethylsilyl)hexyl (TTSH) substituents were transformed into cross-linked materials by UV 193 nm excimer pulsed laser ablation. The process occurred without any catalyst, by reactions of radicals formed in UV laser induced photolysis of side tris(trimethylsilyl)hexyl groups. Chemical changes were monitored by FTIR, LC/UV, GC/MS and solubility tests.     

New models for the prediction of the relaxation behavior of vinyl polymers with bulky side groups and α-methyl groups in the primary transition region

Summary Modified models for the prediction of the slope index of the viscoelastic master curve in the primary transition region for vinyl polymers with either bulky side groups or -methyl groups have been proposed. Very good agreeements between predicted and experimental values are found. The modified models take into account of the effect of the bulky side group or -methyl groups in the contribution to the corrected number of the main-chain atoms. The predicted slope index was found to be proportional to (i) the average cohesive energy per main-chain atom; U/N, which represents the enthalpic interchain interaction, (ii) the entropic intrachain interaction as defined by H/N, and (iii) the average spatial molecular volume per main-chain atom V/N.     

Infrared-spectroscopic investigations of molecular order in liquid crystalline side chain polymers

Summary Infrared dichroism was used to determine the order parameters of liquid crystalline side chain polymers. By this the order parameters of the main chain, of the spacer and of the mesogenic group can be obtained separately. Therefore spectra of two liquid crystalline polyacrylates were recorded with polarized light at different temperatures. In a poly(acrylate) with 6 CH₂ groups in the spacer a high order parameter was found not only for the mesogenic group, but also for the spacer and the main chain. The orientation of the poly(acrylate) with a spacer of only 2 CH₂ groups is lower due to the stronger interaction of main chain and mesogenic group.     

Influence of chirality on phase behaviour of side chain liquid crystalline polymers

Summary Two kinds of chiral side chain liquid crystalline polyacrylates were synthesized and characterized by DSC, POM and x-ray diffraction. The results indicated that chirality of side chain end group and spacer length strongly influence the phase behaviour of the polymers. The polymer P-I with one asymmetric carbon atom of end group exhibits enantitropic Smectic S_A and S_C phases. The polymer P-III having two asymmetric carbon atoms displays enantitropic Smectic S_A and S_B phases. Formation of liquid crystalline polymorphism of polymers depends on spacer length of side chains.     

Synthesis and properties of novel vinyl polymers bearing azacrown ether side chain

Summary Novel vinyl polymers bearing monoazacrown ether-type side chains with a number average molecular weigh of over 5000 were radically synthesized from the 16-membered α-methylenemacrolide monomers. The obtained polymers possessed a Na⁺ or K⁺ selective extraction ability, whereas K⁺ was preferentially extracted by the monomers. The polymer having the N-(2-naphthoyl)azacrown ether pendant groups showed a selective UV-responsive complexation with Li⁺ in 1,2-dichloroethane-CH₃CN.     

Europium‐containing cholesteric liquid crystalline polymers in the side chain

Europium‐containing cholesteric liquid crystalline polymers were graft copolymerized using poly(methylhydrogeno)siloxane, cholesteryl 4‐(allyloxy)benzoate (M₁), cholesteryl acrylate (M₂), and a europium complexes monomer (M₃). The chemical structures of the monomers were characterized by Fourier transform infrared and ¹H‐nuclear magnetic resonance. The mesomorphic properties and phase behavior were investigated by differential scanning calorimetry, thermo gravimetric analysis, polarizing optical microscopy, and X‐ray diffraction. With an increase of europium complexes units in the polymers, the glass transition temperature (T_g) did not change significantly; the isotropic temperature (T_i) and mesophase temperature range (ΔT) decreased. All polymers showed typical cholesteric Grandjean textures, which was confirmed by X‐ray diffraction. The temperatures at which 5% weight loss occurred (T_d) were greater than 300°C for the polymers. The introduction of europium complexes units did not change the liquid crystalline state of polymer systems; on the contrary, the polymers were enabled with the significant luminescent properties. With Eu³⁺ ion contents ranging between 0 and 1.5 mol %, luminescent intensity of polymers gradually increased and luminescent lifetimes were longer than 0.45 ms for the polymers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40866.     

Copolymers possessing dithienothiophene and boron for optoelectronic applications

In this work, copolymers of dithienothiophenes (DTT) and DTT‐4,4‐dioxide (DTT‐S,S‐O₂) with mesitylboron were prepared for optoelectronic applications. Optical and electrochemical investigations were performed giving rise to the band gaps of 2.46–3.21 and 2.18–2.88 eV, respectively. Copolymers possessing DTT‐S,S‐O₂ units demonstrated the lower band gaps. Density functional theory investigations of the model compounds revealed the presence of an intramolecular charge transfer transition between the donor DTT units and the boron acceptor atoms. POLYM. ENG. SCI., 56:1390–1398, 2016. © 2016 Society of Plastics Engineers     

Mesogen-jacketed liquid crystalline polymers substituted with oligo(oxyethylene) as peripheral chain

Mesogen-jacketed liquid crystalline polymer (MJLCP) is a typical rod-shaped macromolecule. Its unique molecular architecture allows one to tune the geometric parameters of the macromolecular rod. Moreover, the rod surface chemistry can be controlled by designing the peripheral groups of the lateral mesogens. In previous work in this system, short alkyl chains have been used and the resultant macromolecular rods therefore have a hydrophobic surface. In this paper, we report using oligo(oxyethylene) groups as the peripheral groups of the lateral mesogens. Poly{{2,5-bis[4-methoxyoligo(oxyethylene)phenyl]oxycarbonyl}styene} (PnEOPCS) with different oligo(oxyethylene) chain length has been synthesized. These oligo(oxyethylene) groups led to macromolecular rods with hydrophilic surface. Differential scanning calorimetry, polarized light microscopy, and one-/two-dimensional wide-angle X-ray diffraction experiments were carried out to study the phase structures and phase behaviors of this series of polymer. The existence of flexible polar groups lowered the glass transition temperatures of PnEOPCS. All polymers studied showed supramolecular columnar nematic or hexatic columnar nematic phase, which arose from the parallel alignment of the polymer supramolecular rods. The diameter of the cylindrical building block increased with increasing the length of the oligo(oxyethylene) groups. The macromolecular rod surface can be further tuned by complexation the oligo(oxyethylene) with lithium salts. Detailed study showed that this complexation also tremendously affected the liquid crystalline phase of the polymer.     

Flexible thin films based on poly(ester imide) materials for optoelectronic applications

A series of high-performance poly(ester imide)s bearing cycloaliphatic moieties was manufactured by a two-step procedure via solution polycondensation of an aromatic–aliphatic dianhydride containing preformed ester units and cyclohexanone ring in the main chain, with various aromatic diamines. The new dianhydride monomer, namely 2-oxocyclohexane-1,3-bis[4,4′-bis(trimellitate)benzylidene] dianhydride, was synthesized by the reaction between 2,6-bis(4-hydroxybenzylidene)cyclohexanone and trimellitic anhydride chloride. The chemical structure of the resulting dianhydride was confirmed by means of Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopies. The poly(ester imide)s from the series exhibited water uptake capacity in the range 3.45–10.09%. The onset temperatures, corresponding to the first detected thermal weight loss in the samples, ranged from 367 to 441 °C. Besides the cycloaliphatic moieties coming from the dianhydride monomer, the other aliphatic segments present in the diamine structures were responsible for improved optical performance in the resulting poly(ester imide)s, the transmittance being higher than 80% at 684 nm. © 2021 Society of Industrial Chemistry.     

Methacrylate based side chain liquid crystalline polymers with pendant cholesterol group: Preparation and investigation of electrical conductivity mechanism

Methacrylate based side‐chain liquid crystalline polymers (SCLCP) bearing cholesterol pendant moieties with various lengths of aliphatic spacer were synthesized and their electrical conductivity mechanism was studied for their possible applications in elastic microelectronic devices. All the polymers exhibited liquid crystalline behavior of broken focal‐conic fan texture of smectic phase. The dielectric properties of polymers were investigated by impedance spectroscopic technique in the frequency range of 100 Hz to 15 MHz at room temperature. Alternating current (AC) conductivity ( ) of the liquid crystalline polymeric films was observed to vary with angular frequency, ω as ω^S with s < 2. Detailed conductivity analysis revealed that the conductivity of the polymeric films follows quantum mechanical tunneling and correlated barrier hoping conductivity mechanisms at low frequency regime, whereas it obeys super linear power law and direct current conductivity mechanisms at high frequency region. The investigation of the SCLC polymeric films helped to propose a model system for their possible potential applications. In the light of this study, the SCLC polymers will be employed as the gate insulator for organic field effect transistor applications, such as large area flexible arrays or as other advanced microelectronic devices that have superior performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45207.     

Dielectric and optical properties of liquid crystalline side chain polymers. A MNDO-analysis

Semiempirical quantum mechanical MNDO-calculations were performed on side chain liquid crystalline polymers to predict their electronic properties and thus their anisotropic dielectric and optical properties. These predictions are compared with the corresponding experimental results. The conclusion is that the predictions are sufficiently accurate, which suggests to use such methods for screening potentially interesting polymer liquid crystals prior to synthesizing them.     

Structure and liquid crystalline phases of amphiphilic side chain polymers in aqueous solution

Functional amphiphilic molecules which form liquid crystalline (l.c.) phases in aqueous solutions, can be polymerized to amphiphilic side chain polymers. Depending on the formation of the polymer backbone via the hydrophobic (type A) or hydrophilic part (type B) of the monomer, it can be differentiated between two polymers. For both types of polymers a model is proposed which explains their micellar association in solution. In aqueous solutions polymers of type A should form normal spherical, rodlike and disc-like micelles, while polymers of type B should form the corresponding reversed micelles. The phase behavior in aqueous solutions is investigated with two model systems of monomer/side chain polymer of type A. It is shown that the polymers exhibit l.c. phases, which are stable within a broader concentration range, as well as to higher temperatures compared to the corresponding monomers. The structures of the l.c. phases are in accordance with the model considerations.