1H NMR and 2D NMR relaxation and wide line measurements in partially deuterated polystyrenes

Solutions of chain- (PS-d₃) and phenyl ring (PS-d₅) deuterated polystyrenes in perdeuterated PS-d₈ have been investigated with ¹H and ²D NMR relaxation and wide line methods. The intra- and intermolecular parts of the ¹H second moments at ?100°C are 3,7 G² and 2,0 G², respectively, for PS-d₃, and 14,7 G² and ca. 0 G², respectively, for PS-d₅. The intermolecular contribution to the ¹H spin lattice relaxation rate, determined at 55 MHz between 150°C and 250°C, is about one third of the total rate in PS-d₃, and negligible in PS-d₅. We suggest that this contribution is caused by rotational fluctuations of the intermolecular H ?H vectors. The intramolecular ¹H- and ²D-relaxation rates indicate that the phenyl group motion is somewhat faster than the rotational segmental motion of the polymer chain.     

NMR study of molecular motion in solid and molten polystyrene: Application of the deuteron dilution technique

The proton spin-lattice relaxation time T₁ was determined at 13,8, 55,2, and 90 MHz in polystyrene (PS-d₀) and polystyrene deuterated at the chain (PS-d₃) and the phenyl groups (PS-d₅), respectively, at temperatures between ?130 and +230°C. Furthermore, T₁ was measured in isotopic mixtures of PS-d₃ and fully deuterated PS-d₈ where a separation into intramolecular and intermolecular contributions was possible through the deuteron dilution technique. Above 130°C, various distributions of correlation times provide a semiquantitative understanding of the different motins seen by the protons of the partially deuterated systems. Rotating frame relaxation times in PS-d₃ and PS-d₅ reveal librational motions in the solid glass (below 100°) where the amplitudes of the phenyl group librations are much larger than those of the chain oscillations, but the correlation times are of the same order of magnitude.     

Beiträge zur polymerisation von 2-isopropenylnaphthalin, 3. Anionische homopolymerisation von 2-isopropenylnaphthalin

The anionic homopolymerization of 2-isoprenylnaphthalene with butyllithium in tetrahydrofuran at –78°C is described. The refractive index increment amounts to dn/dc = 0,2084 ml/g for these polymers in toluene at 25°C and wavelength λ = 436 nm. Determination of the molecular weights by light scattering yielded values between 13 000 and 270 000. The second virial coefficients also determined by light scattering measurements are comparable with the corresponding data of poly(α-methylstyrene). A calibration curve is given for gel permeation chromatography of the poly(2-isoprenylnaphthalene)s, whose polymolecularity indexes M_w/M_n lie between 1,06 and 1,2. Their intrinsic viscosity/molecular weight relationship is [η] = 1,43·10^?2 M^0,663. From ¹H NMR of the α-methyl group fractions of isotactic triads between 30 and 55% are evaluated. The glass transition temperature extrapolated to infinite molecular weight is T_g∞ = 221°C. Above 300°C fast degradation by monomer formation is observed.     

Phosphonic acid esters as thermally latent initiatiors: Initiation process in the polymerization of glycidyl phenyl ether

The initiating species of phosphonic acid esters serving as thermally latent initiators was investigated in the cationic polymerization of glycidyl phenyl ether (GPE). O,O‐Di‐t‐butyl phenylphosphonate ( 1 H ) dissociated into phenylphosphonic acid and isobutene on heating to 150°C. ²H NMR spectroscopic study was carried out to examine the alkyl initiating species in the cationic polymeriaztion of GPE with O,O‐di‐t‐butyl‐d₉ phenylphosphonate ( 1 D ) in the presence of ZnCl₂. A signal based on the t‐butyl‐d₉ group was observed in the obtained polymer. The cationic polymerization of GPE with phosphonic acid was carried out to examine the proton initiating species at 170°C. GPE was converted quantitatively to the corresponding. It was suggested that both the alkyl cation and the proton serve as the initiating species in the cationic polymerization of GPE.     

Configurational dependences of carbon-13 and proton NMR spin-lattice relaxation times of various polymethacrylates

Isotactic and syndiotactic poly(alkyl methacrylate)s (R = CH₃, C₂H₅, isoC₃H₇, n-C₄H₉ and t-C₄H₉) were prepared by anionic mechanism and the spin-lattice relaxation times T₁ of individual carbons and protons were measured mainly in toluene-d₈ by the inversion-recovery Fourier transform (IRFT) method. The T₁'s of the carbons in the isotactic polymers were consistently longer than those of the comparable carbons in the syndiotactic polymers. The ratios of ¹³C-T₁'s for syndiotactic and isotactic polymers were always in the range of ca. 0,4–0,6 for all types of carbons. The ¹³C-T₁'s decreased with an increase in the bulkiness of the ester group in both polymers. From the measurements of the nuclear Overhauser enhancement (NOE) it was found that the spin-lattice relaxations of carbons in polymethacrylates are dominated by ¹³C-¹H dipolar interactions and that the extreme narrowing condition is satisfied at least above 70°C. The effect of solvent on ¹³C-T₁ was also studied. The results of the measurements of ¹H-T₁'s were parallel to those in the carbons' case. It was concluded that the dependence of T₁ upon the configuration of the polymer is mainly caused by the configurational dependence of the segmental mobility of the polymer.     

High temperature demixing of poly(decyl methacrylate) solutions in isooctane and its pressure dependence

Solutions of poly (decyl methacrylate) in isooctane (2,2, 4-trimethylpentane) show lower critical solution temperatures (LCST) that lie well below the thermal degradation of the polymer. The corresponding exothermal theta-temperature (from the Shultz-Flory plot) amounts to 210°C. The increase in solvent quality by pressure turns out to be very pronounced (d T_c/d_p ≈ +1 K/bar). With solutions of the polymer in motor oils, high temperature demixing is unlikely to occur below their boiling point. The theoretical evaluation of published experimental data for 11 different systems exhibiting LCSTs demonstrates the following: Under the equilibrium vapour pressure of the solution high temperature demixing is generally observed withing the temperature interval between T_b, the boiling point of the pure solvent (1 bar), and 1,5 T_b. As T_c - T_b increases, the heats of mixing and the pressure influence on T_c increase, too.     

Deuteron NMR relaxation and molecular motion of polystyrene in solution

Deuteron relaxation times T₁ of polystyrenes deuterated at the backbone (PS-d₃) and the phenyl ring (PS-d₅), respectively, have been measured in solutions of benzene and diethyl malonate as a function of concentration and temperature. We conclude that the motion of the phenyl ring is faster than that of the backbone, the difference being smallest at high temperatures around 180°C. The temperatures dependence is discussed in relation to the activation energies in polystyrene.     

Deuteron NMR study of molecular motion and phase behaviour in a polymer model membrane

Pulsed ²H NMR was used to study the molecular mobility of a polymer model membrane. The polymerizable lipid analogue consists of a quaternary ammonium ion with two C₁₈ alkyl chains and a methacryloyl moiety attached to the hydrophilic head group via an alkyl spacer. The bilayer spacing as obtained from small angle X-ray scattering was found to be 3 nm in the lamellar L_β gel phase of the monomer and 3,5 nm in the polymer indicating an interdigitated structure. The molecular mobility in both the monomer and the polymer below and above the phase transition L_β → L_α was investigated by the NMR lineshapes and the transverse relaxation time T₂ at five positions of the monomeric unit: a methylene group of the spacer, the head group and three methylene groups of the alkyl chains (1-, 2-, and 7-position). In contrast to the monomer a pronounced motional gradient was observed in the polymer, where the spacer is almost completely immobilized, whereas the mobility in the middle of the hydrophobic chains is largely retained. A quantitative analysis of the NMR lineshapes shows a gradual increase of molecular mobility in the polymer above the phase transition due to an increase in both the jump rate and the number of conformational transitions.     

A Remarkably Large Phase‐Transition Effect in a Random Copolymer of Oligo(ethylene glycol) Methyl Ether Methacrylate (OEGMA)500 Induced by the Photochemistry of the 2‐(Hydroxyimino)aldehyde Group

The effect of UV irradiation on the cloud points (CP) of aqueous solutions of a random 1:1 copolymer of oligo(ethylene glycol) methyl ether methacrylate (OEGMA₅₀₀) and a 2‐(hydroxyimino)aldehyde (HIA) functionalized methacrylate is presented. CPs are determined by visible spectroscopy and dynamic light scattering (DLS). ¹H and ¹³C NMR experiments are carried out in D₂O and DMSO‐d₆ on the polymer and on an HIA‐functionalized model of the photoresponsive repeat unit. UV‐irradiated solutions exhibit an unprecedented increase of the phase‐separation temperature for an OEGMA photoresponsive copolymer (10–22 °C, depending on concentration and irradiation conditions). Phase separation is reversible with little hysteresis. With both pristine and irradiated polymer solutions, aggregate dimensions are <10 nm (DLS) at room temperature. Aggregates of >100 nm form at the CP and gradually grow as temperature increases, whereas the light‐induced processes of the repeat unit model in DMSO‐d₆ are well identified (e.g., oxime E/Z isomerization and Norrish‐Yang cyclization of the aldehyde moiety), it is not straightforward to extrapolate such behavior to the polymeric solution in water. The remarkably large phototriggered thermal effect in the present work motivates further investigations on the solvent‐dependent photochemistry of HIA as a promising functional group for the synthesis of multi‐stimuli responsive materials.     

Determination of the Reactivity Ratios for the Oxidative Copolymerizations of Indene with Methyl,Ethyl and Butyl Acrylates

The copolyperoxides of various compositions of indene with methyl acrylate, ethyl acrylate and butyl acrylate have been synthesized by the free‐radical‐initiated oxidative copolymerization. The compositions of copolyperoxide obtained from ¹H and ¹³C NMR spectra have been used to determine the reactivity ratios of the monomers. The copolyperoxides contain a greater proportion of the indene units in random placement. The NMR studies have shown irregularities in the copolyperoxide chain due to the cleavage reactions of the propagating peroxide radical. The thermal analysis by differential scanning calorimetry suggests alternating peroxide units in the copolyperoxide chain. From the activation energy for the thermal degradation, it was inferred that degradation occurs via the dissociation of the peroxide (O—O) bonds of the copolyperoxide chain. The flexibility of the polyperoxides in terms of glass transition temperature (T_g) has also been examined.     

Effect of the alkyl residues on the glass transition temperature of methacrylonitrile/alkyl methacrylate copolymers

The glass transition temperature of copolymers of methacrylonitrile with methyl, ethyl and butyl esters of methacrylic acid, together with those of the corresponding homopolymers, were determined by differential scanning calorimetry. The variation of the glass transition temperature (T_g) of copolymers with the composition of the samples was analyzed for each system on the basis of treatments suggested by Barton, Johnston and Suzuki-Mathot, determining the values of the glass transition temperature of the alternating diad (T_g12). It was observed in all the cases that the alternating diad presents a flexibility higher than that expected from the combination of both kinds of monomeric units according to the T_g of the corresponding homopolymers and that the T_g12 values decrease with the length of the side chain of the methacrylate ester in the system, as the T_g values of the polymethacrylates.     

NLO Behavior of Polymers Containing Y‐Shaped Chromophores

New polyurethanes containing Y‐shaped chromophores, symmetrical derivatives of 4‐(dicyanomethylene)‐2‐methyl‐6‐[p‐(dimethylamino)styryl]‐4H‐pyran, have been prepared. The polymers show high glass transition temperatures (T_g) and a good thermal stability. SHG measurements on poled polymer films of the synthesized polymers have been carried out and a maximum d₃₃ of 15 pm · V^?1 has been found at 1 368 nm fundamental wavelength. Time stability measurements on the most active polymer have shown that after the initial fast relaxation, the d₃₃ value remains constant at 80 °C for 60 d.

     

In Situ Kinetics Reveal the Influence of Solvents and Monomer Structure on the Anionic Ring-Opening Copolymerization of Epoxides

In-depth understanding of copolymerization kinetics and the resulting polymer microstructure is crucial for the design of materials with well-defined properties. Further, insights regarding the impact of solvents on copolymerization kinetics allows for precisely tuned materials. In this regard, in situ ¹H NMR spectroscopy enables precise monitoring of the living anionic ring-opening copolymerization (AROP) of ethylene oxide (EO) with the glycidyl ethers allyl glycidyl ether (AGE) and ethoxy vinyl glycidyl ether (EVGE), respectively. Determination of reactivity ratios reveals slightly higher reactivity of both glycidyl ethers compared to EO, emphasizing a pronounced counterion chelation effect by glycidyl ethers in AROP. Implementation of density functional theory (DFT) calculations further illustrates the complexation capability of ether-containing side groups in glycidyl ethers, in analogy to crown ethers (“crown ether effect”). Investigation of the copolymerization in i) THF-d₈ and ii) DMSO-d₆ shows an increasing disparity of reactivity ratios for both glycidyl ethers compared to EO, clearly related to decreasing solvent polarity.     

Flow properties of concentrated solutions of polyarylate in m-cresol

The flow properties of concentrated solutions of polyarylate from bisphenol A/50:50 isophthalic acid: terephthalic acid in m-cresol are studied. The results are discussed in terms of critical concentration C_c and critical molecular weight M_c for the onset of entanglements. Values of C_c = 8,2 wt.-% and M_c ≈ 3500 are obtained. The dependence of the Newtonian viscosities with temperature allows to obtain different energies of activation of flow for each polyarylate/m-cresol system, ranging from 9 to 13 kcal/mol (= 37,7 to 54,4 kJ/mol). The following free-volume-additivity equation is proposed to fit these data: where E_a, E_ap, and E_ad are the activation energies of the solution, the polymer and the solvent, respectively. V_p and V_d are the polymer volume fraction and the diluent volume fraction, respectively, and α_p and α_d represent the differences between the volume coefficients of expansion above and below the corresponding glass transition temperatures for the polymer and the solvent.     

Solid Polymer Electrolytes, 9

Summary: A new hybrid polymer electrolyte system containing polysiloxane and polyether segments has been designed and prepared by epoxide crosslinking. The thermal behavior, structure and ionic conductivity of the hybrid materials were investigated and characterized by differential scanning calorimetry (DSC), ¹³C solid‐state NMR spectroscopy and alternating current (AC) impedance measurements. Two glass transition temperatures were observed, showing a dependence on the composition and LiClO₄/PC content. The miscibility of the polymer components in the hybrid was studied by examining the ¹H spin relaxation times in the laboratory frame (T₁(H)) and in the rotating frame (T_1ρ(H)) with various compositions. Multi‐relaxation T_1ρ(H) behavior has been observed, indicative of the presence of structural heterogeneity on the timescale of T_1ρ(H). These results are correlated and used to interpret the phenomenon of the conductivity of the lithium ion in the matrix of hybrid networks.

Schematic structure of polysiloxane/polyether networks.     

Calorimetric study of tetrahydro-1,3-oxazin-2-one and poly(oxy-1,3-propanediyliminocarbonyl), and the polymerization/depolymerization equilibrium

In adiabatic vacuum and dynamic calorimeters the temperature dependence of the heat capacity C_p⁰ of tetrahydro-1,3-oxazin-2-one (THO) and poly(oxy-1,3-propanediyliminocarbonyl) (PTHO) was studied between 5 and 500 K. The melting temperature of the monomer and the polymer, the enthalpies of melting of THO and the glass transition temperature of PTHO were determined. In a calorimeter with a static bomb and an isothermal shield the energies of combustion ΔU_comb of the monomer and the polymer were measured. From the experimental data the thermodynamic functions C_p⁰, H⁰(T) – H⁰(O), S⁰(T), G⁰(T) – H⁰(0) were calculated in the range of 0 to 450 K, and enthalpies of combustion ΔH_comb⁰ and thermochemical parameters of formation ΔH_f⁰, ΔS_f⁰, ΔG_f⁰ of the compounds studied were estimated at T = 298.15 K and standard pressure. The results obtained were used to estimated the thermodynamic characteristics of the equilibrium of THO polymerization in bulk (ΔH_pol⁰, ΔS_pol⁰, ΔG_pol⁰), with opening of the six-membered ring and formation of the linear polymer PTHO, in the range 0 to 450 K. It was found that the ΔG_pol⁰ values are always negative and change from ?18 kJ · mol^?1 at 0 K to ?14 kJ · mol^?1 at 450 K. Thus, the process equilibrium is everywhere shifted towards the formation of the polymer. The upper (ceiling) limiting temperature of THO polymerization in bulk at standard pressure is T_ceil = 750 K, that is, considerably higher than the temperature of the onset of the thermal polymer decomposition (450 K).     

Synthesis of Polymers Bearing Oligo‐Aromatic Esters for Second‐Order Nonlinear Optics

We synthesized methacrylate‐type polymers bearing oligo‐aromatic esters as side chains to create unique second‐order nonlinear optical (NLO) active polymers ( PMA n ‐x , PMA n C‐x , PMA2N‐x , and PBA3N‐x , x = oligo‐aromatic ester contents) for the investigation of the resulting architecture. The polymers were obtained from the polymerization of methacrylated oligo‐aromatic esters and the copolymerization of the esters with methyl methacrylate or tert‐butyl methacrylate using a radical initiator. The cut‐off wavelength (λ_co) of these polymers was shorter than the visible region aimed at, i. e. λ_co = ca. 330–370 nm, which is much shorter than λ_co of the typical second‐order NLO polymers containing groups such as azobenzene chromophores. Second‐harmonic generation (SHG) measurements of these polymer films after treatment by corona poling were carried out using the Maker‐fringe method. These polymer films exhibited good transparency in the visible region and a second‐order nonlinear optical coefficient d₃₃ of 2.2–9.8 pm·V^–1. The d₃₃ values of some derivatives decreased with an increase of the chromophore content, which is due to a strong interaction between the side chains with increasing chromophore content.     

Thermodynamics of 5,5-dimethylperhydro-1,3-oxazin-2-one,its polymerization in bulk and poly(5,5-dimethyl-2-oxo-1-oxa-3-azahexamethylene) between 0 K and 500 K

The thermodynamic properties of the six-membered cyclic urethane, viz. 5,5-dimethylperhydro-1,3-oxazin-2-one (DIO, 1 ) and the corresponding polymer, poly(5,5-dimethyl-2-oxo-1-oxa-3-azahexamethylene) (PDIO, 2 ) were studied by calorimetry. The temperature dependence of the heat capacity at constant pressure C_p⁰ of the monomer and the polymer was studied between 5 K and 500 K. Temperatures and enthalpies of physical transitions were determined. The energies of combustion of the above compounds were measured. From the results the thermodynamic functions C_p⁰(T)–H⁰(O), S⁰(T) G⁰(T)–H⁰(O), were calculated for various physical states of the monomer and the polymer from 0 K to 500 K. The standard enthalpies of combustion ΔH_comb⁰ and the thermochemical parameters of formation of DIO and PDIO were estimated at temperature T = 298,15 K and pressure p = 101,325 kPa. The zero entropy S_gt⁰(O) and configurational entropy S_conf⁰ of PDIO in the glassy state were evaluated. The thermodynamic parameters of the bulk polymerization of DIO were calculated in the range of 0 K to 400 K at standard pressure. It was established that an equilibrium of the polymerization reaction of DIO to PDIO is shifted towards the formation of the monomer in the whole temperature range studied from 0 K to 450 K.     

Viscosity and intrinsic viscosity/temperature relationships for dilute solutions of poly(2-biphenylyl methacrylate) and poly(4-biphenylyl methacrylate)

The actual viscosity η and the intrinsic viscosity [η] of six fractions of poly(2-biphenylyl methacrylate) {poly[1-(2-biphenylyloxycarbonyl)-1-methylethylene], (POB); weight average molecular weight M?_w: 4,0 · 10⁴ to 1,42 · 10⁶, polydispersity ratio M?_w/M?_n ≈ 1,4} and of three fractions of poly(4-biphenylyl methacrylate) {poly[1-(4-biphenylyloxycarbonyl)-1-methyl-ethylene], (PPB); M?_w : 8,1 · 10⁴ to 5,3 · 10⁵, M?_w/M?_n ～ 1,4} in benzene have been determined at different temperatures between 20 and 60°C. Values of the apparent activation energy of the viscous flow Q and the pre-exponential term A in the expression η = A · exp[Q/(RT)] have been obtained. Q varies with M?_w and concentration c according to Moore's equation: Q = Q₀ + K_e · M · c, where Q₀ refers to the solvent and K_e depends on polymer and solvent. The numerical value of K_e for POB and PPB is 1,6 · 10^?4 (6,7 · 10^?4) and -8,1 · 10^?4 cal · dl · g^?1 (-3,4 · 10^?3 J · dl · g^?1), resp. From all polymethacrylates studied POB is the only polymer with a positive K_e value. The positive value of K_e for POB may possibly be related to the more extended form of POB in benzene and also may be connected, at least partly, with its low flexibility. The temperature coefficient of the unperturbed dimensions dln〈r₀²〉/dT for POB estimated from the viscosity data using the Burchard-Stockmayer-Fixman relation, is 0,14 · 10^?3, much lower than for PPB (2,3 · 10^?3 between 22 and 40°C and 1,2 · 10^?3 between 40 and 60°C). The positive values of dln〈r₀²〉/dT indicate that extended conformations of these polymers in benzene must be associated with higher energies.     

Towards highly functionalized and semi-rigid polyzwitterions, 1. Poly(dizwitterionic methacrylates): synthesis and specific properties

Monoamino-monozwitterionic (AZ) and dizwitterionic (Z2) methacrylates (CH₂=C(CH₃)— CO[O—(CH₂)₂] _p—(NH—CO)_q—O—CH[CH₂—N⁺(CH₃)₂—O—CO—C^–(CN)₂]₂ as Z2 species) were synthesized by controlled quaternization of their diamino (A2) precursors with 2,2-dicyanoketene ethylene acetal (DCKEA). In absence of a spacer group (p = q = 0), free radical polymerization in homogeneous dimethyl sulfoxide (DMSO) solution is possible only for the AZ monomer but not for the Z2 one, as a result of steric hindrance in the latter case. In presence of a spacer group (p = 0, q = 1 and p = q = 1), polymerization of the Z2 monomers readily leads to high molecular weight polymers (degree of polymerization DP_w > 10³). The poly(dizwitterionic methacrylate) bearing the longer spacer group (p = q = 1) displays specific solution and bulk properties: a) solubility either in highly dipolar aprotic solvents with lower critical solution temperatures (N,N-dimethylacetamide (DMAC): 54°C) and a “salting-in” effect of LiCl or in concentrated aqueous NaSCN solutions (≈ 3 mol·L^–1) with upper critical solution temperatures (dT/d[NaSCN] ≈ –71°C·L·mol^–1); b) slightly reduced chain flexibility characterized by a persistence length of about 30 Å; c) lyotropic behavior in concentrated N,N-dimethylformamide (DMF) solution (local nematic order for a polymer volume fraction φ_P > 0.4); d) ability to dissolve LiClO₄ up to stoichiometric amounts ([LiClO₄]/[zwitterion] = 1) to yield amorphous blends showing glass transition temperatures much lower than that of the pure polymer (T_g = 160°C) and local order likely corresponding to a double-layer lamellar structure.