Nano‐Scale Molecular Shapes of Water‐Soluble Chitin Derivatives Having Monodisperse Poly(2‐alkyl‐2‐oxazoline) Side Chains

The molecular shapes and the sizes of structures formed by chitin derivatives with monodisperse poly(2‐alkyl‐2‐oxazoline) side chains were investigated using atomic force microscopy (AFM), cryo‐transmission electron microscopy (cryo‐TEM), and small‐angle neutron scattering (SANS) analyses. A ring structure with an outside diameter of 45–60 nm and a cross‐sectional diameter of 10–18 nm was observed in the AFM image for chitin‐graft‐poly(2‐methyl‐2‐oxazoline) 1d (DP of the side chain, 8.5; [side chain]/[glucosamine unit], 0.53). From the cryo‐TEM observation of the graft copolymer 1d in 0.5 wt.‐% D₂O solution, an average diameter of 40 nm for the particles was determined, with a narrow size distribution. SANS measurements of the 0.5 wt.‐% D₂O solution of 1d revealed that the outside diameter of the particles and the cross‐sectional diameter were 57 nm and 8 nm, respectively. The absolute weight average molecular weight of 1d was determined to be 5.4 × 10⁵ by static light scattering. From these results it was concluded that 1d can form a unimolecular ring structure in aqueous solution. However, graft copolymers with fewer side chains ( 1c ; [side chain]/[glucosamine unit], 0.30) and with more side chains ( 1e ; [side chain]/[glucosamine unit], 0.96) did not form rings but instead formed monodisperse unimolecular spherical particles of diameters of 28–36 nm by AFM. A graft copolymer 1f with relatively long side chains (DP of side chain, 19.6; [side chain]/[glucosamine unit], 1.00) was also observed as a spherical particle by AFM (diameter: 30–40 nm by AFM; 40 nm by SANS). On the other hand, an intermolecular aggregate formation (diameter of the aggregate: 36–143 nm) was observed for graft copolymers 1a and 1b having short side chains (DP of side chains, 5.6; [side chain]/[glucosamine unit], 0.35 and 0.48, respectively), with a spherical molecular particle of diameter 36 nm by the AFM analysis. Chitin‐graft‐poly(2‐ethyl‐2‐oxazoline) ( 2 ) (DP of side chains, 21.7; [side chain]/[glucosamine unit], 0.95) generated larger aggregates of diameter 100–400 nm by AFM. The complexation behavior of graft copolymer 1d with magnesium 8‐anilino‐1‐naphthalenesulfonate (ANS) and with N‐phenyl‐1‐naphthylamine (PNA) was also examined by fluorescence measurement in an aqueous solution. It was found that graft copolymer 1d complexed with both ANS and PNA, and the binding constants were calculated to be 7.5 × 10⁴ M ^?1 and 5.3 × 10⁴ M ^?1, respectively.

Chemical structure of chitin‐graft‐poly(2‐alkyl‐2‐oxazoline).     

Loose‐Fit Polypseudorotaxanes Fabricated by γ‐CDs Threaded Onto a Single PNIPAAm‐PEG‐PNIPAAm Chain in Aqueous Solution

When γ‐CDs are added to an aqueous solution of PNIPAAm‐b‐PEG‐b‐PNIPAAm block copolymer, they are threaded onto the polymer chains to give loose‐fit polypseudorotaxanes (PPRs). The inclusion complexation shows a marked dependence on the length of the PNIPAAm blocks although the threaded γ‐CDs are preferably located on the central PEG block. The structure of the resulting PPRs is characterized by using XRD, ¹H and ¹³C CP/MAS NMR, TGA FTIR, and DSC analyses. Because of the mismatched fit between the guest polymer chain and the cavity of the host γ‐CDs, these PPRs may be promising in applications as solid stimuli‐responsive materials.     

Anionic synthesis of well‐defined,poly[(styrene)‐block‐(propylene oxide)] block copolymers

Well‐defined, narrow molecular weight distribution (M_w/M_n ≤ 1.1) poly[(styrene)‐block‐(propylene oxide)] block copolymers with relatively high molecular weight poly(propylene oxide) blocks [e. g. M_n (PPO) = 10 000–12 000 g/mol] have been prepared by anionic polymerization. The polystyrene block (M_n = 5 000; M_w/M_n = 1.1) was prepared by alkyllithium‐initiated polymerization of styrene followed by chain‐end functionalization with ethylene oxide and protonation with acidic methanol. The resulting ω‐hydroxyl‐functionalized polystyrene was converted to the corresponding alkali metal salts with alkali metals (Na/K alloy, Rb, Cs) and then used to initiate block polymerization of propylene oxide in tetrahydrofuran. The effects of crown ethers (18‐crown‐6 and dicyclohexano‐24‐crown‐8) and added dimethylsulfoxide were investigated. Chain transfer to the monomer resulted in significant amounts of poly(propylene oxide) formation (50%); however, the diblock molecular weight distributions were narrow. The highest molecular weight poly(propylene oxide) blocks (12 200 g/mol) were obtained in tetrahydrofuran with cesium as counterion without additives.     

Orientation of the Main Chain in Liquid‐Crystalline Side‐Chain Polyesters with Variation of Main‐Chain Spacer Length

Previous X‐ray investigations on liquid‐crystalline side chain polyesters with variable spacer length in the side chain as well as in the main chain led to the assumption that the structure will change qualitatively if the main chain spacer length exceeds a certain value. We obtained indications supporting this assumption by applying two‐dimensional ¹³C NMR. It was shown that for a sample with main chain spacer shorter than the critical length, the main chain segments align perpendicular to the side chains (〈P₂〉 = ?0.46), and for spacer length larger than critical length, the main chain segments preferentially orient themselves parallel to the side chain (〈P₂〉 = 0.28).

Visualization of the main‐chain order as revealed by the values of Table 2 . The opening angle of the cones corresponds to the average angle of deviation as defined in the text.     

Iminoboronate Backbone‐Based Hyperbranched Polymeric Micelles with Fenton‐Like Enhanced ROS Response

Compared to normal cells, there is a relatively high level of reactive oxygen species (ROS) in tumor cells caused by defecting ROS scavenging systems. To this issue, developing ROS‐responsive nanocarriers has been a promising way to cancer therapy. However, it is always difficult for a certain ROS‐responsive nanocarrier to be perfectly triggered due to the complexity of cancerous tissues. Thus, it is pressing to improve the response sensitivity of ROS‐responsive nanocarriers. Herein, the Fenton‐like reaction enhanced ROS response of polymeric nanocarriers of an iminoboronate backbone‐based hyperbranched polymer with metallisable 8‐hyroxyquinoline (HQ) moieties is demonstrated. HQ‐Cu catalytic sites can be formed at the prepared nanocarriers via the complexation of Cu(II) ions and HQ moieties. Upon H₂O₂, hydroxyl radicals (·OH) are quickly generated via the Fenton‐like reaction between H₂O₂ and HQ‐Cu. Then, the oxidative cleavage of iminoboronate moieties can be effectively activated to disrupt the nanocarriers, leading to a rapid release of encapsulated drugs. It is proposed that this kind of polymeric nanocarriers with Cu‐complexed catalyzing‐triggered ROS response may achieve highly effective oxidation therapy.     

Conjugated Side Chain Tuning Effect of Indacenodithieno[3,2‐b]thiophene and Fluoro‐Benzothiadiazole‐Based Regioregular Copolymers for High‐Performance Organic Field‐Effect Transistors

Two regioregular indacenodithieno[3,2‐b ]thiophene and fluoro‐benzothiadiazole‐based donor–acceptor (D–A) type copolymers with different conjugated side chains of hexyl‐phenyl or hexyl‐thienyl are designed and synthesized to study the effects of the side chain on performance of organic field‐effect transistors (OFETs). The effect of the different conjugated side chains on the energy levels, optoelectronic properties, film morphology, and transistors performance as well as the solvent effect on the performance of both D–A copolymers are thoroughly studied. Top‐gate/bottom‐contact OFETs with a hexyl‐thienyl substituted polymer show higher hole mobility up to 0.211 cm² V⁻¹ s⁻¹ than 0.086 cm² V⁻¹ s⁻¹ observed for the polymer with hexyl‐phenyl side chains. In addition, the hexyl‐thienyl substituted side chain polymer shows relatively better stability under bias stress compared to hexyl‐phenyl conjugated side chain. This result sheds light on the impact of conjugated side chain engineering on the performance and stability of OFETs with D–A copolymers.     

Tannic Acid‐Inspired Star‐Like Macromolecules via Temporally Controlled Multi‐Step Potential Electrolysis

Inspired by tea stains, a plant polyphenolic‐based macroinitiator is prepared for the first time by partial modification of tannic acid (TA) with 2‐bromoisobutyryl bromide. In accordance with the “grafting from” methodology, a naturally occurring star‐like polymer with a polar gallotannin core and a hydrophobic poly(n‐butyl acrylate) side arms is synthesized via a simplified electrochemically mediated ATRP (seATRP), utilizing multiple‐step potential electrolysis. To investigate the kinetics of the electrochemical catalytic process triggered by reduction of Cu(II) or Fe(III) catalytic complex in the presence of the multifunctional initiator, cyclic voltammetry measurements are conducted. The naturally derived tannin macromolecule shows narrow MWDs (? = 1.57). Moreover, solvolysis of the star polymer to cleave the side arms and characterize them indicates that all chains grow to the same length (homopolymers with M_w/M_n <1.17), which confirms the well‐controlled seATRP. The structure of the obtained TA‐based systems is characterized microscopically (AFM) and spectroscopically (¹H NMR, FT‐IR). Atomic force microscopy measurements precisely determine the diameters of the obtained star polymers (19.7 ± 3.3 nm). These new star polymers may find biomedical applications as drug delivery systems and antifouling or antimicrobial coatings.     

Stable and Unconventional Conformation of Single PEG Bent γ‐CD‐Based Polypseudorotaxanes

The unexpected formation of polypseudorotaxanes via attaching 2‐bromoisobutyryl groups to both ends of poly(ethylene glycol) (PEG), which leads to the self‐assembly with γ‐cyclodextrins in aqueous solution, is reported in this study. The resulting polypseudorotaxanes exhibit stable and unconventional single PEG bent conformations as evident from XRD, FTIR, GPC, ¹³C CP/MAS, and ¹H NMR analyses. These polypseudorotaxane products are so stable that they can initiate the bulk ATRP of butyl methacrylate to give rise to the same conformational polypseudorotaxanes.     

Cyclodextrins in polymer synthesis: Steric retardation of the free‐radical polymerization in aqueous medium of 4‐vinylbenzaldehyde/methylated β‐cyclodextrin complex

4‐Vinylbenzaldehyde ( 3 ) was complexed with methylated β‐cyclodextrin ( 4 ) (me‐β‐CD) yielding the water soluble host‐guest complex ( 5 ). Radical polymerization was initiated with K₂S₂O₈/Na₂S₂O₅ in water at room temperature and also at 70 °C. The polymerization tendency of this complex ( 5 ) is lower compared to the styrene/me‐β‐CD‐complex ( 7 ). Also copolymerizations of 5 and complexed styrene ( 6 ) at these two temperatures were carried out and the results are discussed in respect to the behavior of the homopolymerization. The resulting polymers ( 8a‐k , 9a , 9b ) were characterized by SEC‐measurements and ¹H NMR spectroscopy. TEM‐measurements of the homopolymers 8f and 8k show differences in the particle size depending on the amount of me‐β‐CD.

TEM recordings of the polymers 8f (left) and 8k (right).     

Synthesis of conjugated poly(acrylene)s with 1,2‐type (η4‐cyclobutadiene)cobalt moieties in the main chain

The synthesis of polymers containing 1,2‐type (η⁴‐cyclobutadiene)cobalt moieties in the main chain (i. e., poly(cyclobutadienecobalt‐1,2‐diyl‐alt‐biphenyl‐4,4′‐diyl)s) is described. Dichloride monomers with (cyclobutadiene)cobalt moieties (i. e., (cyclopentadienyl)[1, 2‐bis(4‐chlorophenyl)‐3, 4‐bis(4‐alkoxyphenyl)]cyclobutadiene cobalts were obtained by the reaction of (4‐chlorophenyl)(4′‐hydroxyphenyl)acetylene with (η⁵‐cyclopentadienyl)bis(triphenylphosphine)cobalt(I) and chromatographic separation over silica gel of a pure 1,2‐isomer followed by the alkylation of the hydroxy groups. The Ni(0)‐mediated dehalogenative polycondensation of the 1,2‐type monomer was carried out at 80°C in benzene under nitrogen to yield polymers which are soluble in common organic solvents. The number average molecular weights (M_n) of the resulting 1,2‐type organocobalt polyarylenes were 8 000–13 600. The polymers with appropriate lateral alkyl chains were found to show a thermotropic liquid crystalline phase in the range of 58–184°C determined by differential scanning calorimetry and the optical measurement using the crossed polarizers.     

Matrix Order Influence on the Non‐Linear Optical Properties of Dispersed Chromophore‐Azopolymer Systems

Azopolymers with moderate non‐linear optical (NLO) response are used as host matrices for a highly efficient molecule. The second harmonic intensity generated at room temperature by these binary systems increases noticeably by adding an irradiation step (406 nm) to the corona poling process. The free volume increase due to “trans‐cis” photoisomerization of the side‐chain azo moieties allows to align the NLO chromophores and causes, at least partially, this enhancement. In order to investigate the role of guest–host interactions on the NLO response, different matrix arrangements have been induced and different d₃₃/d.     

Polymer of Controlled Chain Length Carrying Hydrophilic Galactose Moieties for Immobilization of DNA Probes

The synthesis and the “living” cationic polymerization of a new saccharidic monomer namely the 1,2 : 3,4‐di‐O‐isopropylidene‐6‐O‐(2‐vinyloxy ethyl)‐D ‐galactopyranose have been investigated. The monomer structure has been characterized by ¹H and ¹³C NMR, elemental analysis and mass spectrometry. It has been polymerized with acetaldehyde diethyl acetal/trimethylsilyl iodide as initiating system in presence of ZnCl₂ as co‐initiator. Macromolecules of controlled chain length (from 2 500 g·mol^–1 to 7 500 g·mol^–1) were obtained, bearing protected saccharidic moieties as side‐groups, and aldehyde as ω‐end‐groups which could be turned into amine ω‐end‐groups. Finally, the saccharidic residues were deprotected in order to perform the binding of DNA probes (oligonucleotides) onto the hydrophilic polymer chains through the anomeric site of the galactose moieties.     

Synthesis and Characterization of PNIPAm Core Cross‐Linked Star Polymers and Their Functionalization with Cyclodextrin

Poly(N‐isopropylacrylamide) (PNIPAm) core cross‐linked star (CCS) polymers (s‐(PNIPAm)_n) are synthesized by arm‐first ATRP method. The related synthesis conditions are investigated and optimized. By varying cross‐linker N,N‐methylenebisacrylamide (BIS) concentration, PNIPAm CCS polymers with about 47, 86, and 211 arms are synthesized. Then, under ATRP condition, the “living” sites at the core of s‐(PNIPAm)_n reacting with a monovinyl β‐cyclodextrin (β‐CD) monomer afford β‐CD functionalized s‐(PNIPAm)_n (CDF‐SPNIPAm). The structures of the star polymers are characterized. The results indicate that in CDF‐SPNIPAm, the ratio of β‐CD units to PNIPAm arm numbers could be up to 0.6:1. The fluorescence spectra of star polymer/ANS (8‐­anilino‐1‐naphthalenesulfonic acid ammonium salt hydrate) systems prove that the β‐CD moieties of CDF‐SPNIPAm are available for including guest molecules. By using pH‐sensitive adamantyl (Ada)‐terminated poly(4‐vinylpyridine) (Ada‐P4VP) (synthesized by ATRP strategy) as a model guest macromolecule, the host–guest complexation between β‐CD units of CDF‐SPNIPAm and adamantyl groups of Ada‐P4VP is confirmed via 2D NOESY ¹H NMR and DLS measurements. The results indicate that the presence of the Ada‐P4VP arms provides temperature‐responsive star polymers with pH sensitivity. Therefore, the β‐CD‐functionalized star PNIPAm could provide host macromolecular platform for constructing novel miktoarm star polymers.

     

Benzo[1,2‐b:4,5‐b′]dithiophene‐alt‐terthiophene Copolymers Containing Styryl‐Triphenylamine Side Chains: Synthesis and Photovoltaic Performance Optimization with Fullerene Acceptors

A new two‐dimensional‐conjugated polymer (PBDTT3‐TPA) containing benzodithiophene (BDT) and a side chain isolation comonomer is designed and synthesized. Interestingly, PBDTT3‐TPA is compatible with higher lowest unoccupied molecular level (LUMO) acceptors of indene‐C₆₀ bisadduct (ICBA), and polymer solar cells based on PBDTT3‐TPA/ ICBA show an open‐circuit voltage (V_OC) of ca. 0.80 V and a power conversion efficiency of 2.48% under AM1.5G illumination of at 100 mW cm^?2. Furthermore, the energy loss in the corresponding fullerene acceptor devices is discussed, and the increase in the observed V_OC is explained quantitatively by the up‐shifted LUMO energy of ICBA (0.17 eV) and the reduced saturation current (J_SO) in the blends.

     

Synthesis and 13C CP MAS NMR spectroscopy of cellulose‐graft‐poly(N‐acetylethylenimine)

Starting from homogeneously prepared tosyl celluloses with DS_Tos values ranging from 0.2 to 1.8 poly(N‐acetylethylenimine) was grafted onto the cellulose backbone. Tosyl moieties served as starting centers for the living ring opening polymerization using 2‐methyl‐1,3‐oxazoline as the monomeric unit. The grafted products could be characterized by IR and ¹³C CP MAS NMR spectroscopy clearly indicating the loss of tosyl moieties as well as the occurrence of the N‐acetylethylenimine residues. ¹³C CP MAS NMR spectroscopy was also found to be an efficient tool for the quantification of grafted polymer after determination of the relaxation behavior of the various nuclei. Thus the grafting efficiency could be controlled by the DS_Tos of the starting tosyl celluloses, whereas the amount of monomer showed only a minor influence on the grafting density.     

Glass‐Transition Temperature (Tg) of Free‐Radically Prepared Polyacrylonitrile by Inverse Gas Chromatography, 2. Molecular‐Weight Dependence of Tg of Two Different Types of Aqueous Polymers

The molecular‐weight dependence of the glass‐transition temperature (T_g) of a series of atactic polyacrylonitriles (PAN)s was studied by inverse gas chromatographic (IGC) analysis. PANs having different molecular weights were prepared by either; (i) the addition of isopropyl alcohol as a chain‐transfer agent, or (ii) a scission reaction induced by the addition of alkali (NaOH) to a solution (N,N‐dimethylformamide solution, at 25 °C) of the resulting polymer. The intrinsic viscosity [η] was in the range of 10.9–0.1 (dl · g^?1), which corresponds to a viscosity‐averaged molecular weight (M _v) of 1 590 000–3 000. As part of the results, a side reaction, which saw the conversion of the nitrile (CN) groups of PAN into amide (CONH₂) and/or carboxylic acids (COOH) groups by alkali, was found to occur. The typical molecular‐weight dependence of the T_g in free‐radically prepared PAN was discussed in connection with a chain‐transfer mechanism in an aqueous medium.

Molecular‐weight dependence of the T_g for PAN (WA). An error bar is given by a short vertical arrow.     

Poly(N‐isopropylacrylamide) Networks Conjugated with Gly–Gly–His via a Merrifield Solid‐Phase Peptide Synthesis Technique for Metal‐Ion Recognition

The temperature‐dependent swelling behavior of poly(N‐isopropylacrylamide) and tripeptide Gly–Gly–His (GGH)/poly(NIPAAm) conjugate hydrogel coatings are investigated using a quartz crystal microbalance with dissipation (QCM‐D) while in contact with NaCl, ZnCl₂, NiCl₂, and CuCl₂ solutions. To fabricate the tripeptide conjugated gels, precursor gels of poly(NIPAAm‐co‐3‐aminopropylmethacrylamide[3.5 mol%]) are synthesized via free‐radical polymerization. The metal‐binding tripeptide, GGH, is subsequently synthesized in the gel via a Merrifield solid‐phase peptide synthesis (SPPS) technique, in which the amino group of the copolymer gel provides a functional site to support peptide synthesis. It is found that the logarithm of the transition temperature of the tripeptide GGH/poly(NIPAAm) conjugate hydrogel is proportional to the ionic strength, showing two distinct regions at low and high ionic strengths for the divalent ions. In the low‐ionic‐strength regime, the salting out constants are 0.08, 0.07, and 0.06 M^?1 for Cu²⁺, Ni²⁺, and Zn²⁺, respectively, which follows the known trend for binding of ions to GGH. In the high‐ionic‐strength region, when the metal‐ion binding sites in the tripeptide conjugate hydrogel are saturated, the salting out constants are similar to the salting out constants associated with pure poly(NIPAAm).

     

In vivo T2 relaxation time measurement with echo‐time averaging

The accuracy of metabolite concentrations measured using in vivo proton (¹H) MRS is enhanced following correction for spin–spin (T₂) relaxation effects. In addition, metabolite proton T₂ relaxation times provide unique information regarding cellular environment and molecular mobility. Echo‐time (TE) averaging ¹H MRS involves the collection and averaging of multiple TE steps, which greatly simplifies resulting spectra due to the attenuation of spin‐coupled and macromolecule resonances. Given the simplified spectral appearance and inherent metabolite T₂ relaxation information, the aim of the present proof‐of‐concept study was to develop a novel data processing scheme to estimate metabolite T₂ relaxation times from TE‐averaged ¹H MRS data. Spectral simulations are used to validate the proposed TE‐averaging methods for estimating methyl proton T₂ relaxation times for N‐acetyl aspartate, total creatine, and choline‐containing compounds. The utility of the technique and its reproducibility are demonstrated using data obtained in vivo from the posterior‐occipital cortex of 10 healthy control subjects. Compared with standard methods, distinct advantages of this approach include built‐in macromolecule resonance attenuation, in vivo T₂ estimates closer to reported values when maximum TE ≈ T₂, and the potential for T₂ calculation of metabolite resonances otherwise inseparable in standard ¹H MRS spectra recorded in vivo. Copyright © 2014 John Wiley & Sons, Ltd.     

Surrounding Interactions on Phase Transition Temperature Promoted by Organometallic Complexes in Functionalized Poly(N‐isopropylacrylamide‐co‐dopamine methacrylamide) Copolymers

The functionalization of different structures with organometallic complexes provides exciting properties in terms of applicability due to its ability to provide multiple benefits for catalysis and biomedicine as well as in other fields. This work reports the direct, facile functionalization of copolymers based on N‐isopropylacrylamide and dopamine methacrylamide with bis(cyclopentadienyl)titanium (IV) dichloride (Cp₂TiCl₂, Cp = η⁵‐C₅H₅), which can offer an easy preparation method in comparison with other functionalization procedures. In addition, the lower critical solution temperature (LCST) is studied through aqueous solutions of new structures, which is affected by the presence of the metallocene moieties. UV–vis spectroscopy shows an average of the LCST‐behavior in comparison with rheology that provides essential information about the changes of the phase transition temperature associated with the composition of the polymeric chains and their interactions with the medium. Then, the inclusion of an organometallic complex along the polymeric chain can partially modify the phase transition temperature due to the interactions promoted by the organometallic complex of surroundings over the polymeric sections free of comonomer content.     

Heterofunctionalized Multiarm Star Polymers via Sequential Thiol‐para‐Fluoro and Thiol‐Ene Double “Click” Reactions

The successful postfunctionalization of multiarm star polystyrene (PS) with pentafluorophenyl and allyl moieties at the periphery is demonstrated employing modular thiol‐para‐fluoro and photoinduced radical thiol‐ene double “click” reactions, respectively. α‐Fluoro and α‐allyl functionalized PS (α‐fluoro‐PS and α‐allyl‐PS) are in situ prepared by atom transfer radical polymerization of styrene and their mixture is used as macroinitiator in a crosslinking reaction with divinyl benzene (DVB) yielding (fluoro‐PS)_m–polyDVB–(allyl‐PS)_m multiarm star polymer. It is found that the multiarm star polymer includes nearly identical number of arms possessing pentafluorophenyl and allyl moieties at the periphery. The obtained multiarm star polymer is then reacted with 1‐propanethiol through thiol‐para‐fluoro “click” reaction to give (propyl‐PS)_m–polyDVB–(allyl‐PS)_m multiarm star polymer, which is subsequently reacted with N‐acetyl‐l ‐cysteine methyl ester via radical thiol‐ene “click” reaction in order to give well‐defined heterofunctionalized (propyl‐PS)_m–polyDVB–(cysteine‐PS)_m multiarm star polymer, with higher molecular weight and narrow molecular weight distribution. Multiarm star polymers are characterized by using viscotek triple detection gel permeation chromatography, ¹H, and ¹⁹F NMR.