Monotropic and enantiotropic
Superscript or subscript I, II, I–II, and L mean form I, form II, forms I–II transition, and liquid state, respectively. Form I is the stable form in the case of the monotropic transition, and the stable form at lower temperature in the case of enantiotropic transition. ΔH t and ΔH m are the enthalpies of polymorphic transition and fusion.
Other articles where monotropy is discussed: allotropy: Allotropes may be monotropic, in which case one of the forms is the most stable under all conditions, or enantiotropic, in …
enantiotropic and monotropic. In enantiotropic liquid crystals, we can reach liquid crystalline state either lowering the temperature of the liquid or ...liquid. Thermotropic liquid crystals can be classified into two types: enantiotropic liquid crystals, which can be changed into the liquid crystal state from either lowering the temperature of a liquid or raising of the temperature of a solid, and monotropic liquid crystals, which can only beDownload scientific diagram | Schematic representation of the two types of polymorphs. a Monotropic and b enantiotropic polymorphs, where T 0 denotes the transition temperature in enantiotropic ...Jan 1, 1999 · The thermodynamic terms enantiotropy and monotropy are demonstrated by means of solid‐state analytical results of polymorphous flurbiprofen (FBP). The compounds with even spacer exhibit enantiotropic phase and oligomers with odd parity display monotropic phase. The oligomers with odd membered n = 5, 7 and 11 exhibit N* and SmC* phases upon cooling. ... However, oligomer with outer spacer n = 8 displays enantiotropic N* and SmC* phases. The temperature range of N* phase for even and odd ...
From a thermodynamics point of view, the solid-state polymorphism phenomena can be classified into two categories: monotropic and enantiotropic transition.69 In a monotropic system, the free energy curve of each polymorph will not intersect until the temperature reaches the highest melting point amongst all the …Even-members displayed wider monotropic and enantiotropic N phases, despite the fact that almost all odd-members showed either none or only monotropic-narrower ones. Interestingly, their thermal transition temperatures were lower compared to those for alkoxy (OR) analogues, on account of the small angle (or large bend) of the C-S-C bond as well ...The compound 5OSCl has an enantiotropic nematic phase N and monotropic smectic A phase and 6OSCl is characterised by the existence of two enantiotropic phases, the N and smectic A phases. The compound 11OSNO 2 only exhibits an enantiotropic SmA phase. The permanent dipole moments of the studied molecules are located parallel to their long axes ...A series of random copolyesters containing two different aromatic ester triads and a decamethylene flexible spacer was prepared and characterized for the effect of comonomer composition on glass, crystalline and liquid crystalline state properties. The homopolymer of one of the triads was enantiotropic, but the other was not. However, a copolymer containing 90 …systems: monotropic and enantiotropic. In monotropic systems, one polymorph is more stable than the other at all temperatures below the melting point. In enantiotropic systems, one polymorph is more stable than the other above a certain temperature, and the other polymorph is more stable below this temperature. In addition, some systemsMonotropic and b enantiotropic polymorphs, where T 0 denotes the transition temperature in enantiotropic polymorphs (e.g., sulfur), where below the melting point one polymorph can reversibly ...
Even-members displayed wider monotropic and enantiotropic N phases, despite the fact that almost all odd-members showed either none or only monotropic-narrower ones. Interestingly, their thermal transition temperatures were lower compared to those for alkoxy (OR) analogues, on account of the small angle (or large bend) of the C-S-C bond as well ...Longer chains facilitate microphase separation, consequently inducing and stabilizing additional layered Sm phases and transforming them from monotropic to enantiotropic LCs. The focal conic and fan-shaped textures observed for the SmA phase of 10S–AZO–6 were maintained in its lower-temperature phase and accompanied by subtle changes in the ...1. Monotropic System. Only one polymorph is stable at all reasonable temperatures. e.g. metolazone. 2. Enantiotropic system. One polymorph is stable over one temperature …Pressure and the terminology on dimorphism. Thermodynamic stability relationships between polymorphs are usually inferred from calorimetric data by way of an energy–temperature (E–T or G–T) diagram.The stability behavior of polymorphs is categorized as either enantiotropic or monotropic, based on the tendency of the …Burger and Ramberger [9,10] developed a procedure for the classification of two different types of polymorphic systems (monotropic and enantiotropic) based on thermodynamic rules. Recently, Park ...For a monotropic pair of polymorphs, the relative stability will stay the same below the melting point. Conversely, an enantiotropic system has a transition point below the melting temperature so that the order of the stability for the low-temperature and high-temperature polymorphic pair changes above and below the transition temperature.
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Whereas in series II, compounds containing C1–C8 carbon atoms exhibit only a monotropic smectic phase and compounds with C10, C12, C14, and C16 atoms show an enantiotropic smectic phase.Polymorphism is the ability of solid materials to exist in two or more crystalline forms with different arrangements or conformations of the constituents in the crystal lattice. These polymorphic forms of a drug differ in the physicochemical properties like dissolution and solubility, chemical and physical stability, flowability and hygroscopicity.Thermal properties of mesophase of these liquid crystal compounds were studied to reveal that they all exhibited an enantiotropic nematic phase except for the compound bearing an OH group, i.e ...Difference Between Enantiotropic and Monotropic. ADVERTISEMENT. Definitions. Enantiotropic ...polymorph A. This gives rise to an enantiotropic system of solid phases. For an enantiotropic system, a reversible transition can be observed at a definite transition temperature at which the Figure 1. Variation of energy with temperature for enantiotropic and monotropic systems. Curves H A, H B and H L are for enthalpy, whereas H f,A and H f,BMonotropic systems (A and C, A and B), enantiotropic system (A and B) with a transition temperature T t, and an amorphous and supercooled liquid with a glass transition temperature T g. Melting points, T m , for the crystalline phases are shown by the intersection of the curves for the crystalline and liquid states.
This substance has a monotropic nematic phase at atmospheric pressure. But over a pressure, the nature of isotropic to nematic phase transition changed from monotropic to enantiotropic phase transition. It is the first observation in P-V-T experiments that the monotropic isotropic-nematic transition changes enantiotropic under pressure.polymorph A. This gives rise to an enantiotropic system of solid phases. For an enantiotropic system, a reversible transition can be observed at a definite transition temperature at which the Figure 1. Variation of energy with temperature for enantiotropic and monotropic systems. Curves H A, H B and H L are for enthalpy, whereas H f,A and H f,BThe solubility ratio of the two forms and the DSC thermogram of the orthorhombic form strongly suggest that the system is monotropic. However, according to the polymorph rules of Burger and Ramberger, the estimated higher melting enthalpy and lower melting temperature of the orthorhombic form points towards an enantiotropic system.Furthermore, a series of liquid-crystalline (LC) π-conjugated oligothiophenes bearing three or two alkoxy chains at their extremities have been fabricated [51]. Other than this, thermotropic liquid crystals can be classified into two types: enantiotropic and monotropic. Enantiotropic LCs.Jan 4, 2022 · There are two categorized types of polymorphic transition according to the stability relationship: monotropic and enantiotropic (Yu 1995; Zhang et al. 2004; Lohani et al. 2006). Based on the free energy–temperature diagram shown in Fig. 1 , the two different polymorphic systems, monotropic and enantiotropic, can be clearly distinguished. The LCPA with a spacer of 8 methylene units displays enantiotropic smecticity with an interdigitated molecular packing arrangement over a wide temperature range ... monotropic nematicity, enantiotropic nematicity, and enantiotropic smecticity, depending on the length of the alkylene spacer. The Enyclopedia of Polymer Science and Technology ...Enantiotropic one polymorph can be reversibly changed into another one by varying the temperature or pressure. eg. sulfur 2. Monotropic the change between the two forms is irreversible. eg. What is Monotropic polymorphism? Monotropic relationship occurs when one of polymorphs is stable over entire temperature range (Fig. …After a basic introduction to polymorphism the most useful methods of detection of polymorphism are cited. A selection of typical DSC curves illustrates monotropic and enantiotropic solid—solid transition, allotropy, metastable—stable transition through the liquid state, pseudopolymorphic transition and mesophase transition. In addition ...
12 May 2008 ... Keywords [en]. m-hydroxybenzoic acid, 3-hydroxybenzoic acid, polymorphism, monotropy, enantiotropy, solubility, van't Hoff enthalpy of solution, ...
Sep 16, 2021 · the furfural set are monomorphic exhibiting enantiotropic N mesophases, except for the longest chain member ( F 12 )t h a ti s dimorphic and possesses monotropic smectic A phase and The LCPA with a spacer of 8 methylene units displays enantiotropic smecticity with an interdigitated molecular packing arrangement over a wide temperature range ... monotropic nematicity, enantiotropic nematicity, and enantiotropic smecticity, depending on the length of the alkylene spacer. The Enyclopedia of Polymer Science and Technology ...Assuming the monotropic and enantiotropic relationships between G form I and G form II described above, the heat of fusion rule means that the enthalpy of fusion of form I (ΔH form I) is higher than ΔH form II in a monotropic system, whereas ΔH form I is lower than ΔH form II in an enantiotropic system. The heat of transition from the ...Institute of Solution Chemistry of RAS Artem Surov Institute of Solution Chemistry of RAS Abstract and Figures In this work, a database containing thermochemical and structural information about...The relative stability behavior of the polymorphs I and II has been the subject of considerable study, and some authors favor an enantiotropic [45,46,47,48] and others a monotropic relationship [49,50,51]. Espeau et al. characterize the stability domains of two polymorphs of paracetamol from a thermodynamic point of view. They established the I ...The melting points of the confined crystals decrease monotonically with decreasing pore size, and the enantiotropic phase behavior of bulk glutaric acid and suberic acid switches to monotropic when confined within the nanoscale pores of CPG and p-PCHE. Collectively, these results reveal that nanometer-scale size confinement can alter ...The oligomers with even number of members exhibit monotropic phase in which the compound with n = 4 shows nematic (N) phase whilst those with members n = 6 and 8 exhibit N and smectic A (SmA) phases.
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In the case of an enantiotropic system, one polymorph is stable at a particular temperature and pressure, whereas other polymorphs are stable at many temperatures and pressure; these polymorphs ...For a monotropic pair of polymorphs, the relative stability will stay the same below the melting point. Conversely, an enantiotropic system has a transition point below the melting temperature so that the order of the stability for the low-temperature and high-temperature polymorphic pair changes above and below the transition temperature.For a monotropic pair of polymorphs, the relative stability will stay the same below the melting point. Conversely, an enantiotropic system has a transition point below the melting temperature so that the order of the stability for the low-temperature and high-temperature polymorphic pair changes above and below the transition temperature.18 Tem 2022 ... Monotropic polymorphs are stable across a temperature range, while enantiotropic polymorphs possess a transition temperature at which polymorphs ...Mar 7, 1994 · There are two types of polymorphism, enantiotropic and monotropic. The exothermal solid-solid transition of metastable into the stable form is called monotropic polymorphism (Fig. 1) and can occur only in the direction ss~ss and not in the reverse. The heat of fusion of the earlier melting /3' is smaller than that of /3. The concept of energy/temperature diagrams is introduced, and then applied to enantiotropic and monotropic systems. The alternative representation of phase ...Longer chains facilitate microphase separation, consequently inducing and stabilizing additional layered Sm phases and transforming them from monotropic to enantiotropic LCs. The focal conic and fan-shaped textures observed for the SmA phase of 10S–AZO–6 were maintained in its lower-temperature phase and accompanied by subtle changes in the ...20 Haz 2016 ... Other rules for determining whether a monotropic or an enantiotropic relationship exits are: Enthalpy of fusion rule. When the higher melting ...There are two types of polymorphic systems: monotropic and enantiotropic. In monotropic systems, one polymorph is more stable than the other at all temperatures below the melting point. In enantiotropic systems, one polymorph is more stable than the other above a certain temperature and the other polymorph is more stable below this temperature.The thermodynamic terms enantiotropy and monotropy are demonstrated by means of solid‐state analytical results of polymorphous flurbiprofen (FBP).Recently, I've been studying the subject of polymorphism and met two important concepts, the monotropic and enantiotropic polymorphic transition types. However, I can't really seem to grasp the difference between them practically. What I do understand is that enantiotropic polymorphism is reversible, but what does "reversible" mean practically? ….
Both monotropic and enantiotropic nematic phases were achieved for two homologues from the nonsubstituted (-H) series H-Dn, indicating that the lateral substitution plays an important role in ...Enantiotropic System C, Monotropic System Temperature Temperature tiotropic system on the left, at constant pressure, there are three solubility versus temperature curves: Form II is the lowest, Form I is the next higher, and the melting curve ...Moreover, a homogeneously dispersed LCP may induce an enantiotropic transition in monotropic LCM compounds. In this work, we studied the blends of a flexible nematic LCP with two LCM compounds as model systems. The results indicate that homogenous reinforcement of LCM with LCP is a valid concept and could lead to …J. Ball's 14 research works with 20 citations and 75 reads, including: Molecular simulation and experimental characterisation of monotropic and enantiotropic polymers containing azobenzene and ...Feb 1, 2020 · to enantiotropic or monotropic systems. One of these rules is. the ‘density rule’. It has been proved by numerous studies that. the ‘density rule’ is not very reliable and a number of excep- Polymorphism of trilaurin mixed with 4% of cholesterol was studied with a setup coupling calorimetry and phase characterisation by in-situ X-ray diffraction (Microcalix). Four polymorphic forms were identified. Monotropic and enantiotropic transitions were identified from the reconstruction of Gibbs free energy diagram which allows the control …There are two categorized types of polymorphic transition according to the stability relationship: monotropic and enantiotropic (Yu 1995; Zhang et al. 2004; Lohani et al. 2006). Based on the free energy–temperature diagram shown in Fig. 1 , the two different polymorphic systems, monotropic and enantiotropic, can be clearly distinguished.Research article Full text access Effect of hydrogen bonds on the amorphous phase of a polymer as determined by atomistic molecular modellingDSC measurements indicate that form I behaves monotropic to forms II and III. Desolvation of the 2-propanol solvate at higher temperatures results in a transformation into form II, whereas the removal of 2-propanol at room temperature and in vacuum reduced pressure leads to the formation of form III. ... Disorder, and Enantiotropic Phase ... Monotropic and enantiotropic, [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1], [text-1-1]