Molecular Conformations of Shape Anisometrically Variant Mesogens in Liquid Crystalline Phase Studied by 13C NMR Spectroscopy

Mesogens that vary in shape anisometry have been investigated by ¹³C solid-state NMR in the liquid crystalline phase to inspect the conformations. The molecules examined comprise of (i) rod-like mesogen with three-phenyl ring core and terminal hexyloxy chains, (ii) three-ring core linked to the fourth phenyl ring via a spacer, and (iii) trimesic acid connected to three side arms core units through a spacer. The order parameter (S_zz) values for the phenyl rings of the rod-like mesogen are 0.65–0.68, while the mesogen with a three-ring core linked to a phenyl ring via spacer showed dissimilarity. Consequently, for the core unit phenyl rings, S_zz is ~0.70, and the terminal phenyl ring showed a low value of 0.12. For the trimesic acid based mesogen, the S_zz value for the side arm phenyl rings is ~0.53, and for the central phenyl ring, a very low value of 0.11 is witnessed. By considering the ordering of the rod-like mesogen as a yardstick and employing the ratios of S_zz values of the phenyl rings, the average conformations of other mesogens are arrived. Accordingly, for the trimesic acid based mesogen, a tripod-like conformation instead of λ shape is proposed in the liquid crystalline phase.     

Influence of the Thiophene Ring on the Molecular Order of Structurally Simple π-Conjugated Smectogens: 13C NMR Study

Structurally simple rod-like π-conjugated mesogens with thiophene directly connected to phenyl, biphenyl, and fluorenone rings with terminal chains are synthesized respectively. The occurrence of smectic A/smectic C phases is concurred by a hot-stage optical polarising microscope (HOPM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The static 1D and 2D ¹³C nuclear magnetic resonance (NMR) studies in the liquid crystalline phase are carried out to find the alignment-induced chemical shifts (AIS) and ¹³C−¹H dipolar couplings. The orientational order parameters of the mesogens determined from ¹³C−¹H dipolar couplings disclose that the long axis is not only collinear to the C3−C4 bond of the thiophene ring but also for the local axes of phenyl and biphenyl rings. For fluorenone-based mesogen, the molecular biaxiality is found to be high owing to the increased breadth of the molecule. The study unveils that the orientation of thiophene and the phenyl rings is similar in the current mesogens in stark contrast to mesogens, where thiophene is connected to phenyl rings through linking groups.     

3-Cyano thiophene-based π-conjugated mesogens: XRD and 13C NMR investigations

3-Cyano thiophene-centred π-conjugated mesogens with alkoxy phenyl/biphenyl rings are synthesised by palladium acetate-catalysed direct arylation to investigate the mesophase properties and the molecular order. The synthesised mesogens mostly exhibit smectic A mesophase as confirmed by X-ray diffraction studies. Further, due to the manifestation of π-conjugated core, the mesogens exhibit photo luminescence in solution with emission maxima in the range 425–460 nm. Density functional theory and time-dependent density functional theory calculations of a representative mesogen indicate possible intramolecular charge transfer transition between the biphenyl to 3-cyanothiophene units. Despite structural simplicity, the observation of smectic A phase is attributed to location of strong dipole moment component perpendicular to the long axis of the molecules due to the presence of polar cyano group at 3-position of central thiophene ring. The ¹³C NMR studies are performed in mesophase and using the ¹³C–¹H dipolar couplings determined from 2D separated local field experiment; the order parameters of central thiophene ring and side arm phenyl rings are calculated. Moreover, the order parameter ratios of thiophene and side arm phenyl rings indicate the bent–core nature of the mesogen.     

Structural assignment and molecular order of three-ring mesogen by 13C NMR spectroscopy in mesophase

A homologous series of rod-like molecules with three phenyl rings in the core and terminal alkoxy chains are synthesised from mesogenic two-ring aldehyde by coupling with non-mesogenic 4-alkoxy anilines. The mesophase properties are evaluated with hot-stage optical polarising microscopy and differential scanning calorimetry, and accordingly, all the molecules exhibited enantiotropic nematic and smectic C phases along with monotropic low-temperature smectic phases. For a representative homologue, the existence of smectic C phase is further confirmed by noticing a sharp reflection at small angle region in powder X-ray diffraction which varies with change in temperature. The main focus of the investigation, however, is the clear demonstration of chemical shift assignment of static ¹³C NMR of a representative three-phenyl ring mesogen in smectic C phase. In this novel approach, the static ¹³C NMR spectral data of synthetic mesogenic intermediate namely two-ring aldehyde are utilised for the chemical shift assignment of three-ring mesogens. Further, the orientational order parameter of two-ring aldehyde in smectic A and three-ring mesogen in smectic C phase is carried out by measuring the ¹³C-¹H dipolar couplings by 2D separated local field spectroscopy.     

13C NMR investigations of molecular order of rod-like,bent-core,and thiophene mesogens

In this review, methods to obtain the orientational order of topologically variant molecular mesogens using by one- and two-dimensional (2D) solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy are described. Besides ¹³C chemical shifts, the ¹³C─¹H dipolar couplings measured from 2D-separated local field (SLF) technique are used for computing the order parameters of a variety of mesogens. The investigated molecules are composed of a variable number of rings in the core, that is, core ranging from simply one ring to five rings. Among the mesogens investigated, a special focus has been placed on mesogens with thiophene rings, which are gaining popularity as liquid crystalline organic semiconductors. The replacement of a phenyl ring by thiophene in the core has a dramatic influence on molecular topology, as observed from the measured order parameters. The review highlights the advantages of the 2D SLF method for understanding the local dynamics and for mapping the topology of mesogens through the measured order parameters. SLF NMR studies of as many as 24 molecular mesogens that vary in terms of the molecular structure as well as topology are covered in the review. Order parameters of the rings have been estimated from the ¹³C─¹H dipolar couplings in the nematic, smectic A, smectic C, and tilted hexatic phases as well as in B₁ and B₂ mesophases of various mesogens. It is anticipated that, in the years to come, the 2D SLF method would provide advanced molecular information on structurally complex mesogens that are emerging in liquid crystal science through the incessant efforts of synthetic chemists. The mini review covers the orientational order of topologically variant molecular mesogens determined by 1D and 2D solid-state ¹³C NMR spectroscopy. Accordingly, rod-like, bent-core, and thiophene mesogens were subjected to 2D SLF measurements to get the order parameters from which the topology was established. The replacement of phenyl ring by thiophene and its influence on order parameters as well as on molecular topology is also discussed.     

Mesogen‐controlled ion channel of star‐shaped hard–soft block copolymers for solid‐state lithium‐ion battery

Novel star‐shaped hard–soft triblock copolymers, 4‐arm poly(styrene)‐block‐poly [poly(ethylene glycol) methyl ethyl methacrylate]‐block‐poly{x‐[(4‐cyano‐4′‐biphenyl) oxy] alkyl methacrylate} (4PS‐PPEGMA‐PMAxLC) (x = 3, 10), with different mesogen spacer length are prepared by atom‐transfer radical polymerization. The star copolymers comprised three different parts: a hard polystyrene (PS) core to ensure the good mechanical property of the solid‐state polymer, and a soft, mobile poly[poly(ethylene glycol) methyl ethyl methacrylate] (PPEGMA) middle sphere responsible for the high ionic conductivity of the solid polyelectrolytes, and a poly{x‐[(4‐cyano‐4′‐biphenyl)oxy]alkyl methacrylate} with a birefringent mesogens at the end of each arm to tuning the electrolytes morphology. The star‐shaped hard–soft block copolymers fusing hard PS core with soft PPEGMA segment can form a flexible and transparent film with dimensional stability. Thermal annealing from the liquid crystalline states allows the cyanobiphenyl mesogens to induce a good assembly of hard and soft blocks, consequently obtaining uniform nanoscale microphase separation morphology, and the longer spacer is more helpful than the shorter one. There the ionic conductivity has been improved greatly by the orderly continuous channel for efficient ion transportation, especially at the elevated temperature. The copolymer 4PS‐PPEGMA‐PMA10LC shows ionic conductivity value of 1.3 × 10^?4 S cm^?1 (25 °C) after annealed from liquid crystal state, which is higher than that of 4PS‐PPEGMA electrolyte without mesogen groups. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4341–4350     

Dynamic mechanical and thermal behavior of thermotropic polyesters based on 4,4-alkane-1-ω-diylbis(4-hydroxybenzoic acid) and 4,4-(pentane-1,5-diyloxy)dibenzoic acid

Thermotropic polyesters based on 4,4^′-alkane-1-ω-diylbis(4-hydroxybenzoic acid) and 4,4^′-(pentane-1,5-diyloxy)dibenzoic acid were studied by dynamic mechanical spectroscopy, X-ray scattering, differential scanning calorimetry and polarizing microscopy. The effect of structure changes in the mesogenic group as well as in the flexible spacer, in particular the incorporation of Cl atoms into the mesogen, introduction of ether oxygen into spacer and the number of CH₂ groups in spacer was investigated. More complex mechanical and thermal behaviour was found on second heating scan than on first cooling of the isotropic melt; higher values of mechanical functions were observed in the isotropic state than in the nematic state of melts. While an even number of CH₂ groups and the presence of ether oxygen in spacer shifts the transition temperatures to higher values, the incorporation of Cl atoms into the mesogen leads to disappearance of ordered structure and the polymers behave as amorphous materials.     

Ultrastructure studies of polystyrene-based side-chain liquid-crystalline copolymers containing charge transfer groups

A series of new side-chain liquid-crystalline copolymers has been prepared, and the thermal properties of the individual copolymers have been determined. These copolymers are derived from atactic polystyrene and contain both 4-methoxyazobenzene and 4-nitroazobenzene mesogens; these are linked through octyl spacers to the polystyrene backbone. All the copolymers exhibit a smectic phase that has been assigned smectic A on the basis of polarizing microscopy and x-ray diffraction studies. The glass transition temperatures of the polymers exhibit a linear dependence on composition, whereas the clearing temperatures and the associated entropies show significant deviations from such behavior. The smecticisotropic transition temperatures of the copolymers are higher than those of the composition-weighted averages for the corresponding homopolymers, whereas the entropies of transition are lower than expected. X-ray diffraction studies of fiber samples revealed that the director of the mesophase is oriented perpendicular to the fiber axis. The liquid-crystalline polystyrene containing 25 mol % nitro-substituted mesogen shows an unusual S_A-phase WAXS pattern. The copolymers were investigated further by ¹³C CP/MAS NMR spectroscopy, and the observed changes in the spectra are analyzed in terms of chemical composition and local electronic environment. The application of the interrupted decoupling technique revealed that the spacer contains a number of gauche defects. These observations lead us to suggest possible microstructural arrangements in the smectic phase. © 1993 John Wiley & Sons, Inc.     

Synthesis and curing of novel LC twin epoxy monomers for liquid crystal thermosets

This article describes the synthesis and characterization of new liquid crystalline thermosets having a twin structure. Nematic epoxy-terminated monomers based on a phenyl benzoate twin mesogen connected by an alkylene spacer were synthesized for these studies. In addition, an epoxy-terminated monomer based on a 1,4-bis(benzoyloxy)phenylene mesogen was synthesized to determine the effect of the position of the mesogen on the final network structure. The diepoxy monomer made with phenyl benzoate twin mesogens connected with an alkylene spacer formed a smectic-like network when cured with diamines. This smectic organization appeared even though the diepoxy monomer itself showed only a nematic mesophase over a narrow temperature range. The presence of crosslinks at both ends of the mesogens helped to retain a uniform spacing between crosslinking sites during the curing reaction, and aided formation of the smectic layer arrangement. The epoxy monomer possessing a 1,4-bis(benzoyloxy)phenylene mesogen and two epoxidized alkylene end groups on both sides of the mesogen formed a stable nematic mesophase. However, in contrast to the twin epoxies, the latter epoxy when reacted with diamines tended to produce a nematic-like network which was retained as the crosslinking reaction proceeded. © 1996 John Wiley & Sons, Inc.     

New Architectures for Side Chain Liquid Crystalline Polymers with Chiral Smectic C Mesophases

All attempts at synthesizing side chain liquid crystalline polymers (SCLCPs) with chiral smectic C (s_c*) mesophases simply functionalize one terminal group of the mesogen with a chiral substituent and attach the other terminus to the polymer backbone through a spacer. If a s_c* mesophase is observed, it is usually in the less desirable s_c*-s_A phase sequence. We propose that SCLCPs with laterally attached (vs terminally attached) mesogens offer an ideal architecture for obtaining s_c* meso- phases. This is because extended mesogens symmetrically disubstituted with long n-alkoxy groups can be attached to the polymer backbone through a chiral spacer. Thus, mesogens which typically form the desirable s_c*-n phase sequence can be used, and the chiral group can be introduced at the center of the mesogen which should result in high values of spontaneous polarization. We are not only using mesogens which exhibit s_c*-n phase sequences, but are also attempting to induce smectic layering into laterally attached systems which typically form nematic mesophases by electron-donor-acceptor interactions and immiscible hydrocarbon/fluorocarbon components. Smectic layering was successfully induced in 2,5-bis[(4'-n-alkoxybenzoyl)oxy]toluenes when the n-alkoxy substituents were terminated with perfluorinated segments.     

Substituent effect on azobenzene‐based liquid‐crystalline organophosphorus polymers

An Erratum has been published for this article in Journal of Polymer Science Part A: Polymer Chemistry (2003) 41(23) 3862 A new series of combined‐type, azobenzene‐based organophosphorus liquid‐crystalline polymers were synthesized, and their photoisomerization properties were studied. The prepared polymers contained azobenzene units as both the main‐chain and side‐chain mesogens. Various groups were substituted in the terminal of the side‐chain azobenzene mesogen, and the effects of the substituents were investigated. All the polymers were prepared at the ambient temperature by solution polycondensation with various 4‐substituted phenylazo‐4′‐phenyloxyhexylphosphorodichloridates and 4,4′‐bis(6‐hydroxyhexyloxy) azobenzene. The polymers were characterized with gel permeation chromatography, Fourier transform infrared, and ¹H, ¹³C, and ³¹P NMR spectroscopy. Thermogravimetric analysis revealed that all the polymers had high char yields. The liquid‐crystalline behavior of the polymers was examined with hot‐stage optical polarizing microscopy, and all the polymers showed liquid‐crystalline properties. The formation of a mesophase was confirmed by differential scanning calorimetry (DSC). The DSC data suggested that mesophase stability was better for electron‐withdrawing substituents than for halogens and unsubstituted ones. Ultraviolet irradiation studies indicated that the time taken for the completion of photoisomerization depended on the dipolar moment, size, and donor–acceptor characteristics of the terminal substituents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3188–3196, 2003     

On the liquid-crystalline properties of methacrylic polymers containing 4′-(4-alkyloxyphenyl)azobenzene mesogens

In this article, we report on the synthesis and thermotropic behaviour of methacrylic polymers containing 4′-(4-alkyloxyphenyl)azobenzene mesogens attached to the backbone through n-alkyloxy spacers of 6 or 10 methylene groups. Polymerisations were carried out via free radicals using azobisisobutyronitrile (AIBN) as initiator. Chemical structures of polymers and their precursors were characterised by ¹H NMR spectroscopy. Thermogravimetric analysis showed that azopolymers are thermally stable up to temperatures around 300°C. The thermotropic liquid-crystalline (LC) behaviour was studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffraction (XRD). Results indicate that all synthesised mesogens, monomers and polymers developed two or more orthogonal LC phases in wide temperature ranges. Mesogens and monomers developed nematic and smectic phases, whereas polymers exhibited only smectic phase. In polymers, the arrangement of mesogens depends on the relative length of the spacer and the terminal flexible chain; two distinct structural models were proposed based on chemical interactions and steric constrains. The trans–cis photoisomerisation of monomers and polymers in solution was also studied. High cis-isomer contents (>80%) were reached in relative short irradiation times despite the steric constrains imposed by the polymer backbone.     

Laterally linked mesogens in main chain polymers

The syntheses of liquid-crystalline main chain polyesters with laterally linked mesogens are presented. The terminal groups of the mesogens and the spacers fixation of mesogens, the polyesters with 1,4-di(p-alkoxybenzoyloxy)benzenes 1,4-di(p-alkoxybenzolyloxy)benzenes, 2,5-di(p-alkoxyphenyl)pyrimidines or a 4,4'-bis(p-ethoxyphenylazo)biphenyl derivative. Despite the unusual bilateral fixation of mesogens, the polyesters with 1,4-di(p-alkoxybenzoyloxy)benzenes show mainly monotropic phases which were found to be nematic in investigations with the polarizing microscope, in DSC measurements, temperature-dependent measurements of the Kerr constant and X-ray diffraction experiments. The monotropic nematic character remains when varying the terminal groups of the mesogen as well as the length of the n-alkanedioic acid spacer. However, when the spacer is branched, crystallization can be disturbed effectively and a stable nematic phase can be obtained. All of the polyesters with only 2,5-di(p-alkoxyphenyl)-pyrimidines as mesogens are amorphous. The reason probably lies in the unsymmetric 4,6-substitution of the pyrimidine ring. In contrast to this, oligomers with a 4,4'-bis(p-ethoxyphenylazo)biphenyl derivative show broad, predominantly enantiotropic nematic phases with relatively high clearing temperatures. With the knowledge gained about relations between structure and properties, especially of polyesters with 1,4-(p-alkoxybenzoyloxy)benzenes as mesogens, polyesters with this mesogenic group but with various architectures have been compared. Speculations about possible arrangements of the structural elements have been included to explain the phase behaviour of the polyesters with laterally fixed mesogens.     

Photoinduced alignment of azobenzene side‐chain polymers with short spacer: Biaxial orientation and fast response

Side‐chain azobenzene‐containing liquid crystalline polymer (ALCP) of Poly(6‐[4‐(4‐cyanophenylazo)phenoxy] x‐methylene methacrylate)(Px, x is 2 or 6) was synthesized and used to study its photoinduced alignment behavior irradiated by a linearly polarized laser at room temperature. The relationships between transmittance and irradiation time as well as transmittance and various incident angles were studied in detail. The oversaturation phenomenon of P ₂ film was found to be higher than 1 mW/cm² under irradiation energy density. A model of the biaxial orientation was introduced to explain the phenomenon: it is the rigid short spacer that makes it possible for mesogen to coexist in a way of out‐of‐plane and in‐plane orientation (biaxial orientation), in which the type of photoinduced motions is a single mesogen motion in the film of P ₂ , whereas in the film of P ₆ with longer spacer, the motion is a microdomain motion. The whole domain motion restricted the out‐of‐plane orientation, which shows a slow orientation rate and all mesogens aligned within the film plane. A novel dynamic fitting was also presented to describe the orientation of P ₂ , which was discussed in terms of the fitting parameters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1378–1384, 2006     

Design of calamitic self-assembling reactive mesogenic units: mesomorphic behaviour and rheological characterisation

Several calamitic reactive mesogens containing only two benzene rings in the molecular core and with or without lateral substitution by the methyl/methoxy groups have been designed and their mesomorphic behaviour was characterised. Depending on the molecular structure, some of the materials exhibit the nematic and the orthogonal smectic mesophases. The reactive mesogens are aimed for further design of the macromolecular materials like polysiloxane-based polymers and elastomers. Beyond the mesomorphic and structural properties, the electrorheological properties within the temperature range of the nematic and smectic A mesophases were studied with and without applied electric field for the selected reactive mesogen. The increase of viscosity was found not to be higher than three times under applied electric field strength of 2 kV/mm. The mesomorphic, structural and rheological properties of the newly designed reactive mesogens are discussed in order to contribute to better understanding of the molecular architecture–nano-organisation properties relationship of such mesogenic materials.     

Model liquid crystalline dimers in a slit pore: Monte Carlo simulation study

ABSTRACT

In this work, we present results from (isobaric–isothermal) Monte Carlo Simulation studies of liquid crystalline dimer systems confined in a slit pore. Liquid crystalline dimer systems of various spacer numbers have been considered. Surface-induced conformational and alignment properties of these systems at different pressures under homeotropic anchoring condition have been investigated. We have used easily manageable coarse grained force fields to model both monomer–monomer and monomer–substrate interaction potentials. According to the simulated result, the anchoring of dimers to the surface and orientation of mesogenic units with respect to the surface normal seem to depend on the spacer number for messogen attractive confinement. Dimers with lower spacer number are able be adsorbed to the surface and most of their mesogens are oriented along the surface normal even at lower pressure. Those with larger spacer number are distributed throughout the volume at lower pressure. In the case of mesogen repulsive confinement, most of the dimers are adsorbed to the surface and most mesogens are randomly oriented at low pressure. As the pressure gets higher, the adsorption and orientability increase depending on the type of confinement and spacer number. As a result, clear submolecular partitioning and smectic A like structure have been identified.     

Click procedure of phthalocyanine star-shaped mesogens – the effect of size and spacer length

ABSTRACT

A new Click procedure have been recently presented, in which a mixture of a female piece (star mesogen with shape-persistent conjugated arms and intrinsic free space) and a male building block (the same star mesogen sterically overcrowded with fullerenes attached via spacers to the arms) self-assemble in highly ordered filled liquid crystal structures. This self-assembly is based on the space-filling of the intrinsic free space and the nanosegregation of the fullerenes in helices. Here we highlight the synthesis of larger phthalocyanine star mesogens and fullerenes attached via long spacers and their mixtures as well as mixtures of the components with the stars of intermediate size and spacer length. While the system with long spacers do not show any alignment and π-stacking, the click procedure reappears successfully for the combination of a large female star and the intermediate male star.     

Poly(vinyl ether)s and poly(propenyl ether)s containing mesogenic groups: A new class of side-chain liquid-crystalline polymers

A new series of thermotropic liquid-crystalline polymers, poly(vinyl ether)s and poly(propenyl ether)s, containing the mesogen 4-methoxy-4′-hydroxybiphenyl in the side chain and different spacers between the mesogens and the backbone were synthesized and characterized by DSC and optical microscopy. Their mesomorphic behavior was compared to that of the corresponding polymethacrylates. In general the poly(propenyl ether)s showed lower transition temperatures and larger thermal stability ranges of their mesophases than the respective polymethacrylates, reflecting the effect of substituting the rigid ester bond connecting the spacer to the backbone in polymethacrylates by a more flexible ether bond. Also, poly(propenyl ether)s showed more ordered mesophases than the polymethacrylates, suggesting that a better decoupling of the mesogen and polymer backbone is obtained through the ether linkage.     

Liquid crystalline polymers: 14. Synthesis and thermal behaviour of some polyethers containing azo-mesogens

The paper presents a study on the relationship between the structure of macromolecular chain and its capacity to generate a mesophase, when mesogens with an azobenzene structure are implied. The polymers have been synthesized by phase transfer catalysis starting from 1,9-dichlorononane and different bisphenols: diphenyl-4,4^′-bis[(azo-4-)phenol], 4,4^′-dihydroxyazobenzene, 4,4^′-dihydroxydiphenyl, bisphenol A and 4,4^′-dihydroxybenzophenone. The polymers have been characterized by ¹H-NMR spectroscopy, DSC calorimetry, optical microscopy in polarized light and thermogravimetrical analysis. Theoretical conformational studies, using molecular simulations have also been performed. Due to their particular geometry, bis-(azobenzene) units are better mesogenic groups as compared with the azobenzene ones. The highly aromatic structure makes impossible the samples isotropisation, as the degradation processes starting advance. For these polymers, under UV irradiation, due to the presence of two azo groups in each mesogen unit, strong conformational modifications are expected. The replacement of the bis-(azobenzene) moieties with azobenzene ones reduces the transition temperatures, making possible the samples isotropisation.     

The use of FTIR and NMR spectroscopies to study prepolymerisation interactions in nitrogen heterocycles

A detailed investigation into the functional groups responsible for the formation of a noncovalent complex between 2-aminopyridine (template) and methacrylic acid (functional monomer) has been carried out using FTIR spectroscopy and confirmed by ¹H NMR spectroscopic data. The approach adopted to confirm the mechanism of interaction was the analysis of the template plus the structurally similar 2-methylaminopyridine and 2-dimethylaminopyridine. A 1:1 stoichiometry of complexation was determined by Job plot analysis following titration, with FTIR results complementing those of the ¹H NMR study. The strength of interaction between 2-aminopyridine and the functional monomer measured through band shifts by FTIR spectroscopy was compared with such interactions for the isomers 3- and 4-aminopyridine. This comparison identified a clear correlation between template pK _a, degree of interaction and subsequent nonspecific binding in the nonimprinted polymer. Using FTIR spectroscopy it was also possible to observe the effect of temperature on the prepolymerisation solution. IR spectra showed that lower temperatures led to more stabilized interactions of the hydrogen-bonded complex. The potential advantages of FTIR spectroscopy compared with ¹H NMR spectroscopy in studying prepolymerisation solutions have been identified.