Synthesis, characterization and properties of side-chain pseudopolyrotaxanes consisting of cucurbituril[6] and poly-N-(4-vinylbenzyl)-1,4-diaminobutane dihydrochloride

Pseudopolyrotaxanes 3 is synthesized from cucurbituril[6] (CB[6]) and polymer 2 (poly-N¹-(4-vinylbenzyl)-1,4-diaminobutane dihydrochloride) in water by simple stirring at room temperature. The monomer 1, polymer 2 and pseudopolyrotaxanes 3 are characterized by ¹H NMR, ¹³C NMR, FT-IR and elemental analysis. In 3, the CB[6] beads are localized on tetramethylene units in side chains of 2, and combine N⁺ by noncovalent bonds. The degree of threading (number of CB[6] beads per repeat unit) can be controlled from 0 to 1.0 by controlling the amount of CB[6] added. The properties of polymer 2 and pseudopolyrotaxanes 3 are researched by TGA, X-ray powder diffraction (XRD), environment scanning electron microscope (ESEM) and potentiometric titrations. The pseudopolyrotaxanes have higher thermal stability and chain regularity than the parent polymer which are attributed to the bulkiness and the rigidity of the CB[6] threaded. The decomposition temperature and chain regularity of the pseudopolyrotaxanes increase with increasing amount of CB[6] threaded. The effects of salts (NaCl, NaBr or NaI) to pseudopolyrotaxanes are studied by the transmittance with UV-vis, and the results show that NaI is the satisfied precipitant to the pseudopolyrotaxanes. The surface morphologies of pseudopolyrotaxanes 3 observed by ESEM shows a series of spherical particle with different diameter. The results of potentiometric titrations show that the pseudopolyrotaxanes 3 have larger pK_av and smaller n than polymer 2.     

Ionic pseudopolyrotaxanes bearing a chromophore in the side chain - A spectroscopic study in water

The formation of pseudopolyrotaxanes based on a polyelectrolyte, a surfactant and α-cyclodextrin (α-CD) in aqueous solution is investigated. The polyelectrolyte and the surfactant form an ionic complex the side chains of which interact with each other. These interactions are strongly influenced by the formation of inclusion complexes with α-CD. It is shown by ¹H NMR and UV-vis spectroscopy that threading of the α-CD rings onto the side chains causes a shielding effect which increases the mobility of the side chains. The structure of the pseudopolyrotaxanes is concluded from ROESY spectra and their stoichiometry is determined by Job plots based on shift effects observed in the ¹H NMR spectra.     

Synthesis and properties of block polypseudorotaxanes by threading cucurbit[6]uril

A novel water-soluble block polypseudorotaxane (4) was synthesized in water from cucurbit[n]uril (n?=?6), designated as CB[6], and a block copolymer of methoxy poly(ethylene glycol)-b-poly-[N ¹-(4-vinylbenzyl)-pentane-1,5-diamine dihydrochloride]-b-methoxy poly(ethylene glycol) (P3). Driven by the hydrophobic/hydrophobic interaction and the association between the diamine and glycoluril units, CB[6] beads are localized on the pentamethylene units in the side chains of P3 as found by NMR studies. The degree of threading, i.e., the average number of CB[6] beads per repeat recognition unit of P3, can be controlled from 0.25 to 1.0 by varying the amount of CB[6] added. This molecular feature leads to interesting aggregation behavior of the polypseudorotaxanes in aqueous solutions, as revealed by dynamic light scattering measurements, transmission electron microscopy observations, ultraviolet/visible spectroscopy (UV?Cvis) and fluorescence spectrometry. The average hydrodynamic radius (R _h), the intensity of UV?Cvis absorption band and the fluorescence intensity (I _f) of the block polypseudorotaxanes in solution increase with the increasing of threaded CB[6]. With the solution temperature increasing, the size of the aggregates in water increased and the fluorescence intensity (I _f) of the solution decreased, which shows the polypseudorotaxanes can sensitively respond to temperature changes. This opens the door for the application of the block polypseudorotaxanes in various fields such as drug delivery and controlled release.     

Synthesis and properties of polyacetylenes carrying N-phenylcarbazole and triphenylamine moieties

Novel acetylene monomers containing N-phenyl-substituted carbazole (Cz) and triphenylamine (TPA) groups, namely, 3-ethynyl-9-phenylcarbazole (1) and p-(N,N-diphenylamino)phenylacetylene (2) were synthesized, and polymerized with several Rh-, W-, and Mo-based catalysts. Poly(1) and poly(2) with high number-average molecular weights (15?500-974?000) were obtained in good yields (77-97%), when [(nbd)RhCl]₂-Et₃N (nbd = norbornadiene) was used as a catalyst. The polymers exhibited UV-vis absorption peaks derived from the Cz and TPA moieties at 250-350 nm and polyacetylene backbone above 350 nm. The UV-vis absorption band edge wavelengths of the polymers were longer than those of the corresponding monomers. Poly(2) exhibited a UV-vis absorption peak at a longer wavelength than poly(1) did, which indicates that poly(2) has main chain conjugation longer than that of poly(1). The molecular weights and photoluminescence quantum yields of the polymers obtained by the polymerization using [(nbd)RhCl]₂-Et₃N were larger than those of the Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃]-based counterparts. The cyclic voltammograms of the polymers indicated that they had clear electrochemical properties; the onset oxidation voltage of poly(1) was higher than those of N-alkyl-substituted Cz derivatives. The polymers showed electrochromism and changed the color from pale yellow to blue by application of voltage, presumably caused by the formation of charged polaron at the Cz and TPA moieties. The temperatures for 5% weight loss of the polymers were around 350-420 °C under air, indicating the high thermal stability.     

Synthesis and properties of polyacetylenes having pendent phenylethynylcarbazolyl groups

Novel acetylene monomers substituted with phenylethynylcarbazolyl groups, 3-[(4-octylphenyl)ethynyl]-9-propargylcarbazole (1), 3,6-bis[(4-octylphenyl)ethynyl]-9-propargylcarbazole (2), 9-(4-ethynylphenyl)-3-[(4-octylphenyl)ethynyl]carbazole (3), and 9-(4-ethynylphenyl)-3,6-bis[(4-octylphenyl)ethynyl]carbazole (4) were synthesized, and polymerized with Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃] and WCl₆-n-Bu₄Sn catalysts. The corresponding polyacetylenes with number-average molecular weights ranging from 9200 to 94?000 were obtained in 20-98% yields. The IR spectra of the polymers revealed that acetylene polymerization took place at the terminal ethynyl group, while the ethynylene group remained intact. The UV-vis absorption band edge wavelengths of W-based poly(3) and poly(4) were longer than those of the other polymers. W-Based poly(4) emitted fluorescence with the highest quantum yield (41%). Poly(1) exhibited excimer-based fluorescence in dilute solution.     

Benzoxazines with tolyl, p-hydroxyphenyl or p-carboxyphenyl linkage and the structure-property relationship of resulting thermosets

Three benzoxazines (7-9) with a tolyl, p-hydroxyphenyl or p-carboxyphenyl structure, respectively, were successfully synthesized by a three-pot or two-pot procedure. In the three-pot approach, the first step is the condensation of 2-hydroxybenzaldehyde with p-toluidine, 4-aminophenol and 4-aminobenzoic acid, respectively, forming intermediates (1-3) with an imine linkage. The second step is the addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) on the imine linkage, resulting in intermediates (4-6) with a secondary amine linkage. The last step is the ring closure condensation of (4-6), leading to benzoxazines (7-9). In the simplified two-pot approach, the first two steps-the condensation and imine reduction were carried out in one reactor, so the yield of (4-6) was increased. The structures of monomers (1-9) were characterized and confirmed by 1D and 2D NMR spectra. The synthesized benzoxazines were thermally self-cured or copolymerized with a commercial benzoxazine, bis(3-phenyl-3,4-dihydro-2H-benzo[e][1,3]oxazin-6-yl)methane (F-a). IR analysis was utilized to monitor the ring-opening reaction of (7-9) and to propose the structures of P(7-9). The microstructure and the structure-property relationship of the resulting homopolymers and copolymers are studied.     

Initiator efficiency in ATRP: the tosyl chloride/CuBr/PMDETA system

The low efficiency of p-toluenesulfonyl chloride (TsCl) initiator for the polymerization of methyl methacrylate (MMA), when used in conjunction with N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) and CuBr under atom transfer radical polymerization (ATRP) conditions was investigated. A major by-product in the formation of poly(methyl methacrylate) was identified as N,N-dimethyl-p-toluenesulfonamide (5) and accounted for approximately half of the initiator. Compound 5 was shown to form by the direct reaction of PMDETA and TsCl. In a model experiment equimolar amounts of TsCl, PMDETA and CuBr reacted at 80°C in p-xylene resulted in the formation of 5 and two other unsaturated sulfones 2-methyl-3-[(4-methylphenyl)sulfonyl]-2-propenoic acid methyl ester (6) and 2-[[4-methylphenyl)sulfonyl]methyl]-2-propenoic acid methyl ester (7), formed by the dehydrohalogenation and subsequent isomerization of an intermediate chloro-adduct, 1-(4-methylbenzenesulfonyl)-2-chloro-2-(methyl)methyl propionate (2). Molecular modeling predicted the unsaturated sulfone 7 was thermodynamically more stable than the higher conjugated sulfone 6 and this was confirmed by the isomerization of 6 to 7 at room temperature under mild basic conditions. The absence of 6 and 7 in the polymerization of MMA under ATRP conditions showed that in the early stages of polymerization in the presence of excess MMA, the intermediate chloro-adduct 2 is not formed.     

Ring-opening polymerization of lactide initiated by magnesium and zinc alkoxides

A mono methylether Salen-type ligand, SalenMe-H (1) is prepared in a one flask reaction by condensation of trans-1,2-diaminocyclohexane with 2-methoxybenzenaldehyde and followed by the addition of 2,4-di-tert-butylsalicylaldehyde. Further reaction of 1 with Mg(OBn)₂ in THF produces a magnesium alkoxide, [(SalenMe)Mg(OBn)]₂ (2). Compound 1 reacts with ZnEt₂ yields monomeric complex (SalenMe)ZnEt (3), which further reacts with 1 molar equiv of benzyl alcohol giving [(SalenMe)Zn(OBn)]₂ (4). Experimental results show that complexes 2 and 4 efficiently initiate the ring-opening polymerization of l-lactide and rac-lactide in a controlled fashion, yielding polymers with very low polydispersity indexes. Kinetic studies show a second-order dependency on [LA] and a first-order on [2] with magnesium complex 2 as an initiator. While zinc complex 4 is used as an initiator, the polymerization rate has a first order dependency on both [LA] and [4].     

Mechanistic study of electrochemical oxidation of catechols in the presence of 4-hydroxy-1-methyl-2(1H)-quinolone: Application to the electrochemical synthesis

Electrochemical oxidation of catechols (1a-1c) has been studied in the presence of 4-hydroxy-1-methyl-2(1H)-quinolone (3) as a nucleophile in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the quinones derived from catechols (1a-1c) participate in Michael addition reactions with 3 to form the corresponding benzofuran (or isochromeno[4,3-c]quinoline) derivatives (6a-6c). The electrochemical synthesis of (6a-6c) has been successfully performed in an undivided cell in good yield and purity. The oxidation mechanism was deduced from voltammetric data and by coulometry at controlled-potential. The products have been characterized after purification by IR, ¹H NMR, ¹³C NMR and MS.     

Metallocene-catalyzed synthesis of polyethylenes with side-chain triarylamines: Effects of catalyst structure and triarylamine functionality

The copolymerization of ethylene with 8-triarylamine (TAA) substituted 1-octene monomers (TAA = triphenylamine (M1), N,N-diphenyl-m-tolylamine (M2), N,N-diphenyl-1-naphthylamine (M3)) using various types of group 4 single-site catalytic systems (Cp₂ZrCl₂ (C1), rac-EBIZrCl₂ (C2), rac-SBIZrCl₂ (C3), i-PrCpFluZrCl₂ (C4), Me₂Si(η⁵-C₅Me₄)(η¹-N-^tBu)TiCl₂ (C5)) was investigated to prepare functionalized polyethylene with side-chain TAA groups. The metallocene/methylaluminoxane (MAO) catalytic systems (C1-C4) efficiently lead to the production of high-molecular-weight poly(ethylene-co-M1). While the C4/MAO catalytic system shows the highest comonomer response, the C5/MAO system exhibits the poor compatibility with the M1 comonomer. Copolymerization results of ethylene with M1-M3 using C4/MAO indicate that M1-M3 are well tolerated by both the cationic active species of C4 and MAO cocatalyst, giving rise to the copolymers with high levels of activity and molecular weight. Inspection of the aliphatic region of the ¹³C NMR spectra of the copolymers (P1-P3) having ca. 11 mol% of M1-M3, respectively, reveals the presence of isolated comonomer units with prevailing [EEMEE] monomer sequences in the polymer chain. UV-vis absorption and PL spectra exhibit an apparent low-energy band broadening for P1 and P2 indicative of intrachain aggregate formation. Whereas P2 and P3 undergo completely reversible one-electron oxidation process, P1 shows relatively poor oxidational stability.     

Photosensitive poly(benzoxazole) based on precursor from diphenyl isophthalate and bis(o-aminophenol)

A new synthetic method for the preparation of poly(benzoxazole) (PBO) precursor, poly(o-hydroxyamide) (7) from bis(o-aminophenol) (5) and diphenyl isophthalate (6) has been developed. Polymer 7 was prepared by the polycondensation of 5 and 6 in 1-methyl-2-pyrrolidinone (NMP) at 185-205 °C. Model reactions were carried out in detail to elucidate appropriate conditions for the formation of 2-hydroxybenzanilide (3) from o-aminophenol (1) and phenyl benzoate (2). The photosensitive (PBO) precursor based on polymer 7 containing a 22% of benzoxazole unit and 30 wt% 1-{1,1-bis[4-(2-diazo-1-(2H)naphthalenone-5-sulfonyloxy)phenyl]ethyl}-4-{1-[4-(2-diazo-1(2H)naphthalenone-5-sulfonyloxy)phenyl]methylethyl}benzene (S-DNQ) showed a sensitivity of 110 mJ cm⁻² and a contrast of 5.0 when it was exposed to 436 nm light followed by developing with a 2.38 wt% aqueous tetramethylammonium hydroxide solution at room temperature. A fine positive image featuring 8 μm line and space patterns was observed on the film of the photoresist exposed to 200 mJ cm⁻² of UV-light at 436 nm by the contact mode.     

Synthesis of 1,9-bis[glycidyloxypropyl]penta(1′H,1′H,2′H,2′H-perfluoroalkylmethylsiloxane)s and copolymerization with piperazine

A series of 1,9-bis[glycidyloxypropyl]pentasiloxanes (IV-VI) were prepared by the platinum catalyzed hydrosilylation of 1,9-dihydridodecamethylpentasiloxane (I), 1,9-dihydrido-3,5,7-tris(3′,3′,3′-trifluoropropyl)heptamethylpentasiloxane (II), and 1,9-dihydrido-3,5,7-tris(1′H,1′H,2′H,2′H-perfluorooctyl)heptamethylpentasiloxane (III) with allyl glycidyl ether. Subsequently, IV-VI were copolymerized with piperazine to form high molecular weight copoly(carbosiloxane)s (VII-IX). The structures of the 1,9-bis[glycidyloxypropyl]penta-siloxanes (IV-VI) and copoly(carbosiloxane)s (VII-IX) were determined by ¹H, ¹³C, ²⁹Si, and ¹⁹F NMR as well as IR spectroscopy. The molecular weight distributions (M_w/M_n) of VII-IX have been characterized by gel permeation chromatography and their thermal properties measured by differential scanning calorimetry and thermal gravimetric analysis.     

Electrochemical study of stable N-alkoxyarylaminyl radicals

The electrochemical study of N-tert-butoxy-2,4-diphenyl-6-tert-butylphenylaminyl (1a), N-tert-butoxy-2,4-bis(4-chlorophenyl)-6-tert-butylphenylaminyl (1b), N-[2-(methoxycarbonyl)-2-propyl]-2,4-diphenyl-6-tert-butylphenylaminyl (2), and N-tert-butoxy-2,4,6-tris(4-chlorophenyl)phenylaminyl radicals (3) was performed by cyclic voltammetry using acetonitrile as the solvent and Bu₄NPF₆ as the supporting electrolyte. On cathodic scan (100 mV/s), all the radicals gave chemically reversible cyclic voltammograms, and the were determined to be −1.405 V (1a), −1.310 V (2a), −1.282 V (2b), and −1.195 V (3) (versus Fc⁺/Fc), respectively. On anodic scan (100 mV/s), on the other hand, 1a, 1b and 2 showed chemically reversible cyclic voltammograms, but 3 exhibited a partially reversible couple even on a scan rate of 500 mV/s, indicating that the cation species of 3 was less stable. The determined for 1a, 1b, 2 and 3 were 0.220, 0.280, 0.318 and 0.294 V (versus Fc⁺/Fc), respectively. The electrochemical data were compared with those of thioaminyl radicals, the corresponding sulfur analogues of 1-3.     

Polybinaphthyls incorporating chiral 2,2′-binaphthyl and isoquinoline moieties by Sonogashira reaction

Polymers P-1, P-2, P-3, P-4 and P-5 were synthesized by the polymerization of 5,8-bis(ethynyl)isoquinoline (M-1) with (R)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthyl ((R)-M-2), (S)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthyl ((S)-M-2), (R)-6,6′-dibromo-2,2′-bisbutoxy-1,1′-binaphthyl ((R)-M-3), (S)-6,6′-dibromo-2,2′-bisbutoxy-1,1′-binaphthyl ((S)-M-3), and rac-6,6′-dibromo-2,2′-bisbutoxy-1,1′-binaphthyl (M-4) under Sonogashira reaction, respectively. Both monomers and polymers were analyzed by NMR, MS, FT-IR, UV-vis spectroscopy, DSC-TGA, fluorescence spectroscopy, GPC and circular dichroism (CD) spectroscopy. CD spectra of polymers P-1 and P-2, P-3 and P-4 are almost identical except that they gave opposite signals at each wavelength. The long wavelength CD effect of P-1 and P-2 can be regarded as the more extended conjugated structure in the repeating unit and the helical backbone in the polymer chain. All five polymers have strong blue-green fluorescence due to the efficient energy migration from the extended π-electronic structure of the repeating unit of the polymers to the chiral binaphthyl core and are expected to provide understanding of structure-property relationships of the chiral conjugated polymers.     

Electrochemical characterisation of tetra- and octa-substituted oxo(phthalocyaninato)titanium(IV) complexes

The synthesis and electrochemical characterisation of the following oxotitanium tetra-substituted phthalocyanines are reported: 1,(4)-(tetrabenzyloxyphthalocyaninato)titanium(IV) oxide (5a); 1,(4)-{tetrakis[4-(benzyloxy)phenoxy]phthalocyaninato}titanium(IV) oxide (5b); 2,(3)-(tetrabenzyloxyphthalocyaninato)titanium(IV) oxide (6a) and 2,(3)-{tetrakis[4-(benzyloxy)phenoxy]phthalocyaninato}titanium(IV) oxide (6b). The electrochemical characterisation of complexes octa-substituted with 4-(benzyloxy)phenoxy (9b), phenoxy (9c) and tert-butylphenoxy (9d) groups is also reported. The cyclic voltammograms of the complexes exhibit reversible couples I-III and couple IV is quasi-reversible for complexes 5a, 5b, 6a and 6b. The first two reductions are metal-based processes, confirmed by spectroelectrochemistry to be due to Ti^IVPc²⁻/Ti^IIIPc²⁻ and Ti^IIIPc²⁻/Ti^IIPc²⁻ redox processes and the last two reductions are ring-based processes due to Ti^IIPc²⁻/Ti^IIPc³⁻ and Ti^IIPc³⁻/Ti^IIPc⁴⁻. Chronocoulometry confirmed a one-electron transfer at each reduction step. The electrochemistry of the above complexes is also compared to the previously reported 5c, 5d, 6c and 6d.     

Synthesis and characterization of chiral polythiophenes: Poly [(R)-(−) and (S)-(+)-2-(3′-thienyl)ethyl N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate]

(R)-(−) (1) and (S)-(+)-2-(3′-Thienyl)ethyl N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate (2) monomers were synthesized, characterized, and polymerized in chloroform using FeCl₃ as an oxidizing agent. Molecular weights of 2.6 × 10⁴ and 3.2 × 10⁴ for poly1 and poly2, respectively, were determined by SEC analysis. FTIR spectra of the polymers indicated the coupling of monomers through the α positions. UV-vis spectra showed absorption bands at λ_max = 226 and 423 nm for poly1 and poly2, ascribed to transitions of side groups and polythiophene backbone, respectively. Poly1 and poly2 remained stable up to 210 °C. At higher temperatures, a two step weight loss degradation process was observed for both polymers by TGA analysis. ¹H NMR, in the presence of Eu(tfc)₃, and optical rotation measurements indicate the chiral properties of the monomers 1 ([α]_D²⁸ = −76.2) and 2 ([α]_D²⁸ = +76.0), and the maintenance of chirality after polymerization (poly1 [α]_D²⁸ = −29.0 and poly2 [α]_D²⁸ = +28.4, c = 2.5 in THF). According to scanning electron microscopic analysis, the polymers are highly porous.     

Propylene polymerisations with novel heterogeneous combination metallocene catalyst systems

Propylene was polymerised with novel combination metallocene catalyst systems prepared by an emulsion-based heterogenisation method in liquid monomer conditions. The catalyst combinations investigated were rac-dimethylsilanylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride/rac-[ethylenebis(2-(tert-butyldimethylsiloxy)indenyl)]zirconium dichloride/methylaluminoxane (MAO) (1 + 2) and rac-dimethylsilanylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride/rac-dimethylsilanylbis(2-isopropyl-4-[3,5-dimethylphenyl]indenyl)zirconium dichloride/MAO (1 + 3). The effects of polymerisation temperature and hydrogen on catalyst performance and polymer properties, as well as copolymerisation with hexene and ethylene were investigated. Depending on the polymerisation conditions, M_w of polypropylene varied from 144 to 286 kg/mol for 1 + 2 and from 200 to 390 kg/mol for 1 + 3. Combination 1 + 2 produced broader molecular weight distribution (MWD) than 1 + 3, and a bimodal MWD with clearly separated low- and high-M_w polymer fractions was observed with 1 + 2. The two catalyst systems showed similar hydrogen and hexene responses. Each metallocene precursor showed individual response towards the polymerisation conditions, especially polymerisation temperature, suggesting that interaction between the catalyst active sites was negligible in the studied systems.     

Synthesis of novel poly{methyl-[3-(9-indolyl)propyl]siloxane}-based nonlinear optical polymers via postfunctionalization

A novel series of nonlinear optical (NLO) polysiloxanes with a high density of chromophore moieties based on poly{methyl-[3-(9-indolyl)propyl]siloxane} (PMIPS) were synthesized by a post functional strategy. First, PMIPS (P1) was prepared through hydrosilylation reaction, then P1 is partially formylated by the reaction between P1 and the reagents of dimethylformamide (DMF) and phosphorus oxychloride under the standard Vilsmeier reaction conditions, and these formyl groups with high reactivity are condensed with four predesigned cyanoacetylated chromophores to afford the series of chromophore functionalized polysiloxanes (P3-6). The most special point is the molar concentrations of chromophore moieties are the same in polymers P3-6, which makes it convenient to study the behavior of different chromophores in the polymeric system. The poled films of P3-6 reveal the resonant d₃₃ values in the range of 7.9-55.2 pm/V by second harmonic generation (SHG) measurements.     

Polymeric molecular shuttles: Polypseudorotaxanes & polyrotaxanes based on viologen (paraquat) urethane backbones & bis(p-phenylene)-34-crown-10

Reaction of di(p-isocyanatophenyl)methane (MDI, 4) with N,N′-di(2-hydroxyethyl)- (1b) or N,N′-di[2-(2′-hydroxyethoxy)ethyl]-4,4′-bipyridinium di(hexafluorophosphate) (1e) and other diols [oligo(ethylene glycol)s and poly(tetramethylene oxide)s] in the presence of bis(p-phenylene)-34-crown-10 (2) afforded polyurethane (pseudo)rotaxanes as statistical (7P or 7R) and segmented analogs 10P (P = pseudorotaxane, R = rotaxane). In 7R a bulky alcohol was incorporated at the chain ends and in 13R a bulky diol as in-chain units to form polyrotaxanes and preclude the possibility of dethreading. The crown ether 2 in 10P and 13R was shown by ¹H NMR spectroscopy to be shuttling between the viologen (paraquat) and urethane sites; in DMSO the crown ether prefers the urethane site, probably because of H-bonding with the N–H moieties and complexation of the pyridinium site by the dipolar solvent, while in acetone at low temperatures the viologen site is preferred by the crown ether, with ΔH = −6.91 kcal/mol and ΔS = −22.9 eu for 13R.     

Synthesis and properties of chiral helical polymers based on optically active polybinaphthyls

The chiral polymer P-1 was synthesized by the polymerization of (R)-6,6′-dibutyl-3,3′-diiodo-2,2′-bisoctoxy-1,1′-binaphthyl (R-M-1) with 5,5′-divinyl-2,2′-bipyridine (M-1)via Pd-catalyzed Heck reaction. P-2 and P-2′ were prepared by Wittig-Horner reaction of (R)-6,6′-dibutyl-2,2′-bisoctoxy-1,1′-binaphthyl-3,3′-dicarbaldehyde (R-M-2) with 5,5′-bis (diethylphosphonomethyl)-2,2′-bipyridine (M-2) in the presence of EtONa or NaH, respectively. P-3 was synthesized by Wittig-Horner reaction of (R)-6,6′-di(4-trifluoromethylphenyl)-2,2′-bisoctoxy-1,1′-binaphthyl-3,3′-dicarbaldehyde (R-M-3) with M-2 using NaH as a base. The four polymers have strong blue-green fluorescence due to the extended π-electronic structure between the chiral model compounds (R)-6,6′-dibutyl-/di(4-trifluoromethylphenyl)-2,2′-bisoctoxy-1,1′-binaphthyl (R-1 or R-2) and the conjugated linker 2,2′-bipyridyl group via vinylene bridge. Both monomers and polymers were analyzed by NMR, MS, FT-IR, UV-vis spectroscopy, DSC-TGA, fluorescence spectroscopy, GPC and circular dichroism (CD) spectroscopy. Based on the great differences of specific rotation values and CD spectra, P-1 and P-2 may adopt a zigzag chain configuration, while P-2′ and P-3 may adopt a helical configuration. The responsive optical properties of the two chiral helical polymers P-2′ and P-3 on transition metal ions were investigated by fluorescence, UV-vis and CD spectra. The results show that Ag⁺ and Ni²⁺ lead to nearly complete fluorescence quenching of P-2′ and P-3, Cu²⁺ and Fe²⁺ can cause obvious fluorescence quenching, but Zn²⁺ and Cd²⁺ can only produce slight fluorescence quenching. Ag⁺, Ni²⁺, Cu²⁺ and Fe²⁺ can also lead to the obvious changes of UV-vis spectra of P-2′ and P-3. On the contrary, Zn²⁺ and Cd²⁺ cause little changes. Most importantly, the CD intensities and wavelengths of the chiral helical polymers P-2′ and P-3 exhibit the pronounced changes upon addition of Ag⁺ and Ni²⁺.