Number Of Methylene Spacers Research Articles

Synthesis of Imidazolium Cations Linked to Para-t-Butylcalix[4]arene Frameworks and Their Use as Synthons for Nickel-NHC Complexes Tethered to Calix[4]arenes.

A series of cationic p-tert-butylcalix[4]arenes, with side-arms that are functionalized with imidazolium groups, have been synthesized in good yields. The parent tetrahydroxy para-t-butyl-calix[4]arene was dialkylated at the phenolic hydrogen atoms using α,ω-dibromo-alkanes to yield bis(mono-brominated) alkoxy-chains of variable length. The brominated side-arms in these compounds were then further alkylated with substituted imidazoles (N-methylimidazole, N-(2,4,6-trimethyl-phenyl)imidazole, or N-(2,6-di-isopropylphenyl)imidazole) to yield a series of dicationic calixarenes with two imidazolium groups tethered, via different numbers of methylene spacers (n = 2-4), to the calixarene moiety. Related tetracationic compounds, which contain four imidazolium units linked to the calix[4]arene backbone, were also prepared. In all of these compounds, the NMR data show that the calixarenes adopted a cone configuration. All molecules were characterized by NMR spectroscopy and by MS studies. Single crystal X-ray diffraction studies were attempted on many mono-crystals of these cations, but significant disorder problems, partly caused by occluded solvent in the lattice, and lack of crystallinity resulting from partial solvent loss, precluded the good resolution of most X-ray structures. Eventually, good structural data were obtained from an unusually disordered single crystal of 5a, (1,3)-Cone-5,11,17,23-tetra-t-butyl-25,27-di-hydroxy-26,28-di-[2-(N-2,6-diisopropylphenyl-imidazolium)ethoxy]calix[4]arene dibromide and its presumed structure was confirmed. The structure revealed the presence of H-bonded interactions and some evidence of π-stacking. Some of these imidazolium salts were reacted with nickelocene to form the nickel N-heterocyclic carbene (NHC) complexes 7a-7d. A bis-carbene nickel complex 8 was also isolated and its structure was established by single crystal X-ray diffraction studies. The structure was disordered and not of high quality, but the structural data corroborated the spectroscopic data.

Effect of spacer lengths on the interplay of intrachain and interchain in polynorbornene homopolymers embedded with polyhedral oligomeric silsesquioxane (POSS): A molecular simulation approach

Molecular models of polynorbornene homopolymers, with POSS (polyhedral oligomeric silsesquioxane) group linked to the side chain via various numbers of methylene spacers, were constructed and named as P-m-POSS (where m represents the number of methylene units that connect amide and POSS end group on the side chain, m = 0, 4, and 9), respectively. By molecular mechanics (MM) and molecular dynamics (MD) simulation methods, molecular geometry, chain mobility and packing characteristics were investigated to elucidate the complex interplay of intrachain and interchain in homopolymers dependent on various methylene spacer lengths of the side chain. With short spacer length containing less number of methylene units, the synergetic mobility of the main chain and the side chain can be observed in P-0-POSS by analysis of mean square displacement (MSD), denoting an intrachain coupling restraint within molecule. It is also noticed that the disorganization of twisted side chains surrounding the main chain results in a loose and irregular packing in P-0-POSS, validated by the amorphous morphology in experiment. As the spacer length increased with more methylene units in P-4-POSS, side chains with the highest mobility are partially stretched and independent of the main chain, suggesting the invalidation of intrachain coupling restraint. Furthermore, with the longest spacer length containing 9 methylene units, fully stretched side chains are decoupled from the main chain and have a tendency to be close to each other in P-9-POSS. The interchain correlation between side chains in P-9-POSS facilitates a distinctively regular interdigitation in bulk structure, resulting in the highest crystallinity in experiment.

Renewable (Bis)pyrrolidone Based Monomers as Components for Thermally Curable and Enzymatically Depolymerizable 2-Oxazoline Thermoset Resins

In this study we describe the synthesis of bis(pyrrolidone) based dicarboxylic acids from itaconic acid and their application in 2-oxazoline resins for fully renewable thermoset materials. The monomers are obtained using a bulk aza-Michael addition of a diamine and two itaconic acid molecules using a catalytic amount of water. The monomers can be isolated in high purity after recrystallization, though their yield proved to be highly dependent on the selected diamine spacer length: In general, only the dicarboxylic acids containing diamines with an even number of methylene spacers are isolated in high yields. Through NMR, GPC, and FTIR analysis we demonstrate that these bis(pyrrolidone) based dicarboxylic acids exhibit significantly enhanced curing rates in 2-oxazoline resins compared to resins containing aliphatic dicarboxylic acids such as sebacic acid. Overall, we demonstrate that the rate of 2-oxazoline ring-opening addition with carboxylic acid functionalities is determined by the used dicarboxylic acid, whereas the ring-opening addition of the 2-oxazoline functionality with amide groups is determined by the used bis(2-oxazoline) compound. The thermosets obtained after curing proved to be readily plasticized by water, opening up possibilities for enzymatic degradation.

Synthesis, thermal, and photo alignment behavior of polyethylene imines having nitro substituent azobenzene side chain group

AbstractPolyethylene imines having nitro substituent azobenzene side chain group with different methylene spacer groups (PEImN) were successfully synthesized and characterized by differential scanning calorimetry, polarized optical microscopic, and X‐ray diffraction analysis. All synthesized polyethylene imines showed liquid crystalline properties and the glass transition temperature (Tg) of PEImN decreased as the number of methylene spacers increased. Melting temperatures (Tm) of synthesized PEImN showed an odd‐even effect. Photochemical, thermo‐optical, as well as photo alignment behavior of PEImN were investigated and out‐of‐plane orientational behavior of polymeric films was dependent on number of methylene spacers and polyethylene imines having higher number of methylene spacers (six or more) showed high order parameter values that revealed the well pronounced tendency for the development of out‐of‐plane order from random state on annealing. And the molecular orientation of PEImN between random and out‐of‐plane structures has been achieved by the combination of thermal and photochemical processes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis and Properties of Thermotropic Liquid Crystalline Polyesters with Flexible Polymethylene Spacer

Polymethylene bis(p-hydroxybenzoates) were prepared from methyl p-hydroxybenzoate and different diols by melted transesterification reaction. Three liquid crystalline polyesters were synthesized from terephthaloyl dichloride and polymethylene bis(p-hydroxybenzoates). Its structure, morphology and properties were characterized by Ubbelohde viscometer, Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimetry (DSC), polarized optical microscopy (POM) with a hot stage, and wide-angle X-ray diffraction (WAXD). Results indicated that the intrinsic viscosities were between 0.088 and 0.210 dL/g. Optical microscopy showed that the TLCP has a highly threaded liquid crystalline texture and a high birefringent schlieren texture character of nematic phase and has wider mesophase temperature ranges for all polyesters. DSC analysis were found that the melting point (Tm), isotropic temperature (Ti) of TLCPs decreased and the temperature range of the liquid crystalline phase became wider with increased number of methylene spacers in the polyester. The WAXD results showed that TLCPs owned two strong diffraction peaks at 2θ near 19° and 23°.

OPTICAL SWITCHING OF ERYTHROSINE B BASED POLY (METHACRYLATE) FILMS

Erythrosine B based poly (methacrylate) films with varying even number of methylene spacers have been prepared by the free radical polymerization method. All optical switching and beam deflection effects of polymer films have been investigated by using Nd :YAG laser (532 nm) as a pump beam and a He – Ne laser (632.8 nm) as a probe beam. The nonlinear refractive indices of polymer films are determined using the Z-scan technique. The optical switching and beam deflection effects are due to the change of the refractive index of polymer under the pump beam. The experimental results show that erythrosine B based poly (methacrylate) films have potential application in optical switching.

CHARACTERIZATION AND OPTICAL LIMITING EFFECT OF XANTHENES DYE-BASED SIDE CHAIN POLY(METHACRYLATE) FILMS

Investigation of nonlinear absorption coefficient of eosin blue dye based side chain poly(methacrylate) films is presented using diode pumped Nd:YAG laser radiation (λ=532 nm ) and the Z-scan technique. The effect of the concentration in polymer film and the increase in the number of methylene spacers, hooked to the eosin blue dye, on the nonlinear absorption coefficient is also discussed. It is shown that the nonlinear absorption coefficient in samples is due to the two-photon absorption effect. Moreover, the optical limiting characteristics of polymers film are explored.

Azo dye based poly(alkyloxymethacrylate)s and their spacer effect on optical data storage

Two series of new sudan dye based poly(alkyloxymethacrylate)s were synthesized with varying even number of methylene spacers. The structure of the polymers was confirmed by FT-IR, 1H and 13C-NMR spectroscopy. Thermal stability, glass transition and melting temperatures of the polymers were investigated with thermogravimetric analysis and differential scanning calorimetry respectively. Thermal stability of the polymers decrease with the increasing chain length of the methylene chain. The substituent on the azo moiety in the pendant side chain polymers has less thermal stability than the unsubstituted counterpart. The optical characterization of the polymers was done by formation of the holographic grating using 514.5 nm line of the Ar ion laser as source. The diffraction efficiency of the grating on the polymeric film was studied by varying the length of the methylene spacer, concentration and writing beam power.

Synthesis, characterization and photolysis studies on liquid crystalline poly[4-(4′- x-biphenyl)yl-4″-( m-methacryloyloxyalkyloxy) cinnamate]’s

Three series of side chain liquid crystalline polymers containing terminally substituted biphenyl cinnamoyl esters were synthesized and characterized. The para position in the cinnamoyl group was connected with polymer backbone through various even numbers of methylene spacers. The terminal electron acceptor and donor substituted biphenyl groups were linked to cinnamoyl group through ester linkages. Polarizing microscopic and DSC studies confirm the formation of thermotropic mesophase up on heating. All the polymers exhibited nematic/grainy mesophases. The TGA and DSC studies showed that the nature of the terminal substituents have significant effect on mesophase temperatures as well as in thermal stability of these liquid crystalline polymers. UV light promoted photocrosslinking studies reveal that the clear involvement on photocrosslinking efficiency, although they are linked to the olefinic bond of cinnamoyl group through their ester linkage. It is observed that electron-donating group accelerate the photocrosslinking rate, while acceptor group retard the phase of the reaction on the other hand, the unsubstituted polymers show an intermediate rate.

Synthesis of fluorous trialkyl phosphines with the complete exclusion of PH 3

A novel synthetic protocol has been developed for the synthesis of fluorous tertiary phosphines excluding the use of hazardous PH 3 and with control over the number of methylene spacers and the length of fluorous ponytails.

Eosin blue dye based poly(methacrylate) films for data storage

Eosin dye based poly(methacrylates) with variation in the number of methylene spacers have been prepared by free radical polymerization process. The utility of the polymers for high-density optical data storage using holography has been studied by grating formation with the 514.5 nm line of the Argon ion laser as source. The influence of various parameters on the diffraction efficiency of the polymers has been studied. The effect of increase in the number of methylene spacers, hooked to the eosin blue dye, on the diffraction efficiency of the grating formed has also been discussed. Optical microscopic observations showing grating formation in the polymers have also been presented.

Structures and Phase Transformations of Asymmetric Bent Main-Chain Liquid Crystalline Polyesters

A series of new asymmetric bent main-chain liquid crystalline (LC) polyesters (BPE-Cn) were synthesized through the condensation polymerization of A−B type asymmetric α,ω-carboxylic acid−hydroxyl-terminated monomers containing different even numbers of methylene spacers (BPCA-Cn-PmOH, where n = 6, 8, and 10). Differential scanning calorimetry results showed three phase transition processes in this series of BPE-Cn samples. The phase change with the lowest transition temperature is cooling rate dependent, while the two higher temperature transitions are cooling rate independent. One-dimensional (1D) powder wide-angle X-ray diffraction (WAXD) results at different temperatures revealed that during cooling this series of polymers exhibits a low-ordered LC phase and a highly ordered smectic crystal phase before developing a crystalline phase at lower temperatures. The phase structures and symmetry were identified by 2D WAXD and selected area electron diffraction (SAED). On the basis of 2D fiber WAXD patterns, the low ordered LC phase was identified to be an anticlinically tilted SmC (SmCA) phase, which was constructed by an alternating synclinic SmC phase in each chemical repeating unit layer along the fiber drawn direction. The highly ordered smectic phase was an anticlinically tilted SmH (SmHA) phase, which was again constructed by an alternating synclinic SmH phase in neighboring layers. On the basis of the crystallographic point of view, this smectic crystal phase had an orthorhombic unit cell. The crystalline structure was determined to be an orthorhombic unit cell (KO) with Pna21 symmetry in these three polyesters. The crystalline structures and symmetry were also confirmed by SAED experiments. As the number of methylene units increased, the dimensions of the crystal structures also increased, yet they retained a zigzag conformation. A two-chain packing model of the KO phase with four chemical repeating units was proposed on the basis of the experimental diffraction patterns and qualitatively supported by simulated structural diffractions. Additionally, the phase identifications were also supported by the observation of texture changes in polarized light microscopy. Even though the zigzag molecular arrangement remains in the low ordered SmCA and the highly ordered SmHA phases which mimics the bent-core small molecules, chiral characteristics such as helical supramolecular structures are not observed due to the covalent bonding connections in this series of BPE-Cn polymers.

Odd−Even Effect of the Methylene Chain Number in the Template Polymerization of α,β-Diacetylenecarboxylates Incorporated in Layered Double Hydroxide Clay

The present investigation reports on the significant differences observed in the efficiency of the polymerization depending on the odd- or even-numbered methylene chains of diacetylenecarboxylates, CH3(CH2)(m-1)C[triple bond]C-C[triple bond]C(CH2)(n-1)CO2- (mono-[m,n]), incorporated in layered double hydroxide (LDH) clay. Upon gamma-ray irradiation of the diacetylenecarboxylates, or mono-[m,n], in LDH clay, polymer hybrids or poly-[m,n]/LDH, which exhibited coloring from light orange to violet, were obtained. The color of the poly-[m,n]/LDH hybrids was strongly dependent on the extent of the polymerization degrees. Moreover, the polymerization degrees were controlled by the number of methylene spacers n between the carboxyl and diacetylene groups. An odd-numbered n for the methylene chain of mono-[m,n] was found to be the determining factor in the efficient polymerization of these self-assembling aggregates within the interlayers of LDH clay.

Modular Synthesis of Fluorous Trialkylphosphines.

A modular synthetic protocol was developed for the preparation of fluorous trialkylphosphines with a different number of methylene spacers and various lengths of the fluorous ponytails P[(CH2)ARFX]...

Modular Synthesis of Fluorous Trialkylphosphines

A modular synthetic protocol was developed for the preparation of fluorous trialkylphosphines with a different number of methylene spacers and various lengths of the fluorous ponytails P[(CH(2))(A)R(FX)][(CH(2))(B)R(FY)][(CH(2))(C)R(FZ)] (A, B, C = 3 and 4; X, Y, Z = 4, 6, and 8). [reaction: see text]

Novel thermotropic liquid crystalline polyphosphonates

Main chain liquid crystalline polyphosphonates containing semi-flexible phenylester mesogen with even number of methylene spacers (2–10) have been synthesized. The monomers and polymers were characterized by IR, 1H, 13C and 31P NMR spectroscopy. The spectral details are in accordance with the structures. All the polymers were exhibited liquid crystalline property in the Hot stage optical polarized microscope (HOPM). DSC thermal analysis confirms the mesophase formation for all the polymers. The grain size of the liquid crystalline mesophase is increasing with increasing methylene chain. T g, T m and T i of the polymers decreased with increase in spacer length. The T g of these phosphorus-containing polymers is much lower than that of non-phosphorus polymers containing triad ester mesogens. Energy minimized structures for the molecules which mimic the polymer chain suggests that the reduction in T g may be due to entanglement raised by incorporation of phosphorus heterogeneity.

Effect of ethylphosphate on azobenzene-containing thermotropic liquid-crystalline polymers

A new series of liquid-crystalline polymers with azobenzene mesogens and an even number of methylene spacers along with phosphorus heterogeneity were synthesized. The structures of the monomers and polymers were characterized with various spectral techniques. The thermal analyses were performed with thermogravimetric analysis and differential scanning calorimetry (DSC). The formation of the liquid-crystalline phase was confirmed with hot-stage optical polarizing microscopy. All the polymers exhibited grainy and nematic textures during melting; this was confirmed by DSC analysis. The char yield of the polymers was quite high and was related to the formation of phosphoric acid. The glass-transition temperature, melting temperature, and isotropization temperature were quite low. The reduction in the transition temperature could be attributed to the incorporation of the phosphorus heterogeneity and pendant ethyl group. Molecular modeling studies supported the experimental data obtained. The suitability of these polymers for optical data storage was studied with ultraviolet spectroscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 455–462, 2004

FUNCTIONAL TELECHELIC POLYMER SYNTHESIS VIA ADMET POLYMERIZATION

ABSTRACT Acyclic Diene METathesis (ADMET) polymerization of 1,9-decadiene with epoxy-containing monoolefins using ruthenium based Grubbs' catalyst gave epoxy terminated telechelic polymers. The number of methylene spacers between the olefin and the epoxy from the oxygen side of the epoxy-containing monoolefins was varied from one to three. The optimal condition for the present ADMET polymerization was determined as monomer/catalyst ratio of 200/1 for 96 hr at 90°C. All polymer structures were characterized by FT-IR and 1H NMR spectroscopy. It is quite interesting that even 1,2-epoxy-4-pentene with one methylene spacer metathesizes successfully using ruthenium catalyst despite this monoolefin suffers a stronger negative neighboring group effect than the other monoolefins. The telechelic polymer was reacted with toluene diisocyanate to give a higher molecular weight segmented copolymer connected with oxazolidone linkage.

STUDIES ON ODD-EVEN EFFECT OF METHYLENE SPACERS IN POLY(PYROMELLITIMIDE-URETHANE)S

Three series of poly(pyromellitimide-urethanes)s were synthesized from various N,N′ -bis(ω-hydroxyalkyl)pyromellitimides (HAPMIs) and various dicarbooxyloxyl diazides namely terephthaloyl diazide (TPDA), 4,4′ -diphenyldiacid azide (BPDAA) and 4,4′ -azobenzenediacid azide by solution polycondensation in DMSO at 75°C in the presence of di-n-butyltin dilaurate as catalyst. The polymers were characterized by elemental analysis,IR, 1H and 13C-NMR and X-ray diffraction analysis. Thermalstability and phase transition behavior were studied by TGA, DSC, and hot-stage optical polarized microscopy (HOPM). Tg values decrease linearly as the number of methylene spacer increases while Tm shows odd-even effect. In a given series, polymers with even number of methylene spacers possess higher Tm values than the neighboring polymers with odd number of methylene spacers and thermal stability decreases with increase in number of methylene spacers. Thermal stability is also influenced by the aromatic segment present in the polymer backbone, order being : phenyl > biphenyl > azobenzene.

SYNTHESIS OF ESTER TERMINATED TELECHELIC POLYMER VIA ADMET POLYMERIZATION

Ester terminated telechelic polymers were synthesized by the Acyclic Diene METathesis (ADMET) polymerization of 1,9-decadiene with ester-containing monoolefins using ruthenium based Grubbs catalyst. The number of methylene spacers between the olefin and the ester from the oxygen side of the ester-containing monoolefins were varied from one to three. The optimal condition of the present ADMET polymerization was determined as monomer/catalyst ratio of 400/1 for 72 hours at 90°C. All polymer structures were characterized by FT-IR and 1H-NMR spectroscopy. It is quite interesting that even allyl n-butyrate with one methylene spacer metathesizes successfully using ruthenium catalyst despite this monoolefin suffers stronger negative neighboring group effect than the other monoolefins. Mechanism of the ADMET polymerization of 1,9-decadiene with ester-containing monoolefin was examined comparing the reactions for each of the monomers. Deprotection of terminal ester group was successful to give alcohol terminated telechelic polymer which is useful for production of block copolymer.