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2003 Volume 21 Issue 2
2003, 21(2): 117-121
Abstract:
Linear homopolymer chains in poor solvent exist either as individual crumpled single chain globules or asmacroscopic precipitate, depending on whether the solution is in the one- or the two-phase region. However, linearheteropolymer chains in dilute solution might be able to form stable mesoglobules made up of a limited number of chains ifthe degree of amphiphilicity of the chain is sufficiently high and the experimental conditions are appropriate. The self-assembly of block copolymers in a selective solvent is typical of such examples.In practice,the formation of stable mesoglobules can be directly related to the formation of novel polymeric nanoparticles in solution.In this article,we will address the formation of mesoglobular phase not only on the basis of thermodynamics,but also from a kinetic point of view,which leads to the discussion of how viscoelasticity can affect the phase behavior of heteropolymer chains in dilute solution.The formation and stabilization of several different kinds of novel polymeric nanoparticles will be used to illustrate our discussion.
Linear homopolymer chains in poor solvent exist either as individual crumpled single chain globules or asmacroscopic precipitate, depending on whether the solution is in the one- or the two-phase region. However, linearheteropolymer chains in dilute solution might be able to form stable mesoglobules made up of a limited number of chains ifthe degree of amphiphilicity of the chain is sufficiently high and the experimental conditions are appropriate. The self-assembly of block copolymers in a selective solvent is typical of such examples.In practice,the formation of stable mesoglobules can be directly related to the formation of novel polymeric nanoparticles in solution.In this article,we will address the formation of mesoglobular phase not only on the basis of thermodynamics,but also from a kinetic point of view,which leads to the discussion of how viscoelasticity can affect the phase behavior of heteropolymer chains in dilute solution.The formation and stabilization of several different kinds of novel polymeric nanoparticles will be used to illustrate our discussion.
2003, 21(2): 123-127
Abstract:
It has been a long-standing question whether dewetting of polymer film from non-wettable substrate surfaceswherein the bicontinuous morphology never forms in the dewetting film is due to spinodal instability or heterogeneousnucleation. In this experiment, we use a simple method to make the distinction through introduction of topographical defectsof the films by rubbing the sample surface with a rayon cloth. Spinodal dewetting is identified for those films that dewet by acharateristic wavevector, q*, independent of the density of rubbing-induced defects.Heterogeneous nucleation,on the other hand,is identified for those with q* increasing with increasing density of defects.Our result shows that PS films on oxide coated silicon with thickness less than ≈13 nm are dominated by spinodal dewetting,but the thicker films are dominated by nucleation dewetting.We also confirm that spinodal dewetting does not necessarily lead to a bicontinuous morphology in the dewetting film,contrary to the classic theory of Cahn.
It has been a long-standing question whether dewetting of polymer film from non-wettable substrate surfaceswherein the bicontinuous morphology never forms in the dewetting film is due to spinodal instability or heterogeneousnucleation. In this experiment, we use a simple method to make the distinction through introduction of topographical defectsof the films by rubbing the sample surface with a rayon cloth. Spinodal dewetting is identified for those films that dewet by acharateristic wavevector, q*, independent of the density of rubbing-induced defects.Heterogeneous nucleation,on the other hand,is identified for those with q* increasing with increasing density of defects.Our result shows that PS films on oxide coated silicon with thickness less than ≈13 nm are dominated by spinodal dewetting,but the thicker films are dominated by nucleation dewetting.We also confirm that spinodal dewetting does not necessarily lead to a bicontinuous morphology in the dewetting film,contrary to the classic theory of Cahn.
2003, 21(2): 129-133
Abstract:
The brittle-ductile transition (BDT) of particlc toughened polymers was extensively studied in terms ofmorphology, strain rate, and temperature. The calculation results showed that both the critical interparticle distance (IDc) andthe brittle-ductile transition temperature (TBD) of polymers were a function of strain rate. The IDc reduced nonlinearly withincreasing strain rate, whereas TBD increased considerably with increasing strain rate. The effects of temperature andplasticizer concentration on BDT were discussed using a percolation model.The results were in agreement with the experiments.
The brittle-ductile transition (BDT) of particlc toughened polymers was extensively studied in terms ofmorphology, strain rate, and temperature. The calculation results showed that both the critical interparticle distance (IDc) andthe brittle-ductile transition temperature (TBD) of polymers were a function of strain rate. The IDc reduced nonlinearly withincreasing strain rate, whereas TBD increased considerably with increasing strain rate. The effects of temperature andplasticizer concentration on BDT were discussed using a percolation model.The results were in agreement with the experiments.
2003, 21(2): 135-140
Abstract:
Atomic force microscopy images taken during the crystallization of polyethylene both from processed andquiescent melts are presented. Crystallization from processed melts provides further evidence of a region in front of agrowing lamella that is influenced by the crystallization process, but extending only 40 nm into the melt. High-resolutionimages of the growing crystal tip, taken during crystallization, show no direct evidence of the existence of intermediatephases. The growing tip is shown to be slightly rounded.In-filling crystallization,occurring after the initial flush of growth,is imaged in polyethylene for the first time,and shown to continue to a temperature 8℃ below the initial crystallization temperature.
Atomic force microscopy images taken during the crystallization of polyethylene both from processed andquiescent melts are presented. Crystallization from processed melts provides further evidence of a region in front of agrowing lamella that is influenced by the crystallization process, but extending only 40 nm into the melt. High-resolutionimages of the growing crystal tip, taken during crystallization, show no direct evidence of the existence of intermediatephases. The growing tip is shown to be slightly rounded.In-filling crystallization,occurring after the initial flush of growth,is imaged in polyethylene for the first time,and shown to continue to a temperature 8℃ below the initial crystallization temperature.
2003, 21(2): 141-146
Abstract:
In this study, it was examined whether the dynamics of polymer chains at a surface is different from that in thebulk, and if so, to what extent they differ in terms of surface glass transition temperature and diffusion coefficient. Obtainedresults clearly indicate that surface chains can travel for a relatively large distance in comparison with the characteristiclength scale of usual segmental motion even at a temperature below its bulk glass transition temperature, Tgb. This isconsistent with our previous results that the surface glass transition temperature is much lower than the correspoding Tgb.Also,it was experimentally revealed that there was a gradient of molecular motion in the surface region.
In this study, it was examined whether the dynamics of polymer chains at a surface is different from that in thebulk, and if so, to what extent they differ in terms of surface glass transition temperature and diffusion coefficient. Obtainedresults clearly indicate that surface chains can travel for a relatively large distance in comparison with the characteristiclength scale of usual segmental motion even at a temperature below its bulk glass transition temperature, Tgb. This isconsistent with our previous results that the surface glass transition temperature is much lower than the correspoding Tgb.Also,it was experimentally revealed that there was a gradient of molecular motion in the surface region.
2003, 21(2): 147-152
Abstract:
A series of near infrared (NIR) absorbing dinuclear ruthenium dicarbonylhydrazine complexes (DCH-Ru),[{Ru(bpy)2)2μ-DCH]n+ (where bpy = 2,2'-bipyridinc and n = 2, 3 or 4), were prepared. The DCH-Ru complexes areelectrochromic in the NIR region with a high absorption coefficient at 1550-1600 nm typically over 10000 M-1cm-1. DCH-Ru complex polymers with good NIR electrochromic properties were also obtained and processed to make a device foroptical attenuation at a wavelength of 1550 nm. The potential of these DCH-Ru polymers for use in a variable optical attenuator has been demonstrated with an attenuating power at the 1550-nm telecommunication wavelength over 7.0 dB per micron of polymer film thickness.Other classes of NIR active materials are the pentacenediquinones and the corresponding poly(ether pentacenediquinone)s.These polymers can be electrochemically reduced to the corresponding semiquinone (radical anion )having NIR absorption within a telecom window(e.g.,1310 nm).
A series of near infrared (NIR) absorbing dinuclear ruthenium dicarbonylhydrazine complexes (DCH-Ru),[{Ru(bpy)2)2μ-DCH]n+ (where bpy = 2,2'-bipyridinc and n = 2, 3 or 4), were prepared. The DCH-Ru complexes areelectrochromic in the NIR region with a high absorption coefficient at 1550-1600 nm typically over 10000 M-1cm-1. DCH-Ru complex polymers with good NIR electrochromic properties were also obtained and processed to make a device foroptical attenuation at a wavelength of 1550 nm. The potential of these DCH-Ru polymers for use in a variable optical attenuator has been demonstrated with an attenuating power at the 1550-nm telecommunication wavelength over 7.0 dB per micron of polymer film thickness.Other classes of NIR active materials are the pentacenediquinones and the corresponding poly(ether pentacenediquinone)s.These polymers can be electrochemically reduced to the corresponding semiquinone (radical anion )having NIR absorption within a telecom window(e.g.,1310 nm).
2003, 21(2): 153-158
Abstract:
A series of block copolymers consisting of an isotropic (polystyrene) block and a side-chain liquid crystallineblock (LC) have been studied using small-angle X-ray scattering and dielectric spectroscopy. The triblock copolymer (PS-LC-PS) displays an order-to-order transition (OOT) together with the isotropic/nematic transition of the LC phase. The seriesof diblock copolymers show no clear OOT but the phase diagram differs from that of non-LC block copolymers. The segmental dynamics as measured with dielectric spectroscopy is dominated by the α and δ relaxation of the LC block.Both display a WLF like temperature dependence.The relaxation times are influenced by the constraints of the nanoscale domains.They are decreased for the LC confined in the domain as compared to the LC in the continuous matrix.
A series of block copolymers consisting of an isotropic (polystyrene) block and a side-chain liquid crystallineblock (LC) have been studied using small-angle X-ray scattering and dielectric spectroscopy. The triblock copolymer (PS-LC-PS) displays an order-to-order transition (OOT) together with the isotropic/nematic transition of the LC phase. The seriesof diblock copolymers show no clear OOT but the phase diagram differs from that of non-LC block copolymers. The segmental dynamics as measured with dielectric spectroscopy is dominated by the α and δ relaxation of the LC block.Both display a WLF like temperature dependence.The relaxation times are influenced by the constraints of the nanoscale domains.They are decreased for the LC confined in the domain as compared to the LC in the continuous matrix.
2003, 21(2): 159-167
Abstract:
Structure and properties of bioabsorbable polyglycolide (PGA) and poly(glycolide-co-lactide) (PGA-co-PLA)fibers were investigated during several industrial processing stages and in vitro degradation by means of wide-angle X-raydiffraction (WAXD), dynamic mechanical analysis (DMA) and mechanical property tests. In the orientation stage, the PGA fibers were found to have higher degrees of crystallinity than corresponding PGA-co-PLA samples produced under similar conditions. In the hot-stretching and post-annealing stages,after fibers were braided,PGA samples were found to gain more crystallinity and higher Tg than PGA-co-PLA samples.The higher crystallinity in PGA fibers resulted in a slower rate of degradation.DMA results showed that a great deal of internal stress that was built during orientation and hot-stretching stages was released in the post-annealing stage for all PGA and PGA-co-PLA samples.During earlier stages of in vitro degradation,both PGA and PGA-co-PLA samples exhibited the typical cleavage-induced crystallization mechanism.The heat shrinkage in the glass transition area was found to disappear after 6-8 days of degradation for all PGA and PGA-co-PLA samples,indicating the amorphous portions of the polymers lost orientation after a short period in the buffer solution,most likely due to relaxation of the cleaved chains.
Structure and properties of bioabsorbable polyglycolide (PGA) and poly(glycolide-co-lactide) (PGA-co-PLA)fibers were investigated during several industrial processing stages and in vitro degradation by means of wide-angle X-raydiffraction (WAXD), dynamic mechanical analysis (DMA) and mechanical property tests. In the orientation stage, the PGA fibers were found to have higher degrees of crystallinity than corresponding PGA-co-PLA samples produced under similar conditions. In the hot-stretching and post-annealing stages,after fibers were braided,PGA samples were found to gain more crystallinity and higher Tg than PGA-co-PLA samples.The higher crystallinity in PGA fibers resulted in a slower rate of degradation.DMA results showed that a great deal of internal stress that was built during orientation and hot-stretching stages was released in the post-annealing stage for all PGA and PGA-co-PLA samples.During earlier stages of in vitro degradation,both PGA and PGA-co-PLA samples exhibited the typical cleavage-induced crystallization mechanism.The heat shrinkage in the glass transition area was found to disappear after 6-8 days of degradation for all PGA and PGA-co-PLA samples,indicating the amorphous portions of the polymers lost orientation after a short period in the buffer solution,most likely due to relaxation of the cleaved chains.
2003, 21(2): 169-174
Abstract:
We succeeded in performing of hybrid Scanning Probe Microscopy (hybrid-SPM) in which mechanical-SPM andfluorescence microscopy are combined. This technique is able to measure simultaneously mechanical properties anddistribution of cytoskeletons of living cells by using green fluorescent protein. We measured evolution of both local elasticityand distributions of actin stress fibers in an identical fibroblast living in physiological conditions. The SPM experimentsrevealed that stiffer lines develop in living cells,which correspond to actin stress fibers.The elasticity of the actin stress fibers is as high as 100 kPa.We discuss mechanical effects on the development of actin filament networks.
We succeeded in performing of hybrid Scanning Probe Microscopy (hybrid-SPM) in which mechanical-SPM andfluorescence microscopy are combined. This technique is able to measure simultaneously mechanical properties anddistribution of cytoskeletons of living cells by using green fluorescent protein. We measured evolution of both local elasticityand distributions of actin stress fibers in an identical fibroblast living in physiological conditions. The SPM experimentsrevealed that stiffer lines develop in living cells,which correspond to actin stress fibers.The elasticity of the actin stress fibers is as high as 100 kPa.We discuss mechanical effects on the development of actin filament networks.
2003, 21(2): 175-180
Abstract:
Meso-structured (opal and inverse opal) polymeric hydrogels of varied morphology and composition wereprepared by using two methods: post-modification of the template-synthesized structured polymers and template-polymerization of functional monomers. A polyacrylic acid based inverse opal hydrogel was chosen to demonstrate its fastpH response by changing color, which is important in designing tunable photonic crystals. Template effects of the hydrogelson controlling structure of the template-synthesized inorganic materials were discussed.The catalytic effect of acid groups in the templates was emphasized for a preferential formation of TiO2 in the region containing acid groups,which allowed duplicating inorganic colloidal crystals from colloidal crystal hydrogels(or macroporous products from macroporous hydrogels) via one step duplication.
Meso-structured (opal and inverse opal) polymeric hydrogels of varied morphology and composition wereprepared by using two methods: post-modification of the template-synthesized structured polymers and template-polymerization of functional monomers. A polyacrylic acid based inverse opal hydrogel was chosen to demonstrate its fastpH response by changing color, which is important in designing tunable photonic crystals. Template effects of the hydrogelson controlling structure of the template-synthesized inorganic materials were discussed.The catalytic effect of acid groups in the templates was emphasized for a preferential formation of TiO2 in the region containing acid groups,which allowed duplicating inorganic colloidal crystals from colloidal crystal hydrogels(or macroporous products from macroporous hydrogels) via one step duplication.
2003, 21(2): 189-204
Abstract:
The morphology and crytal structure of poly(p-phenylene terephthalate) (PPT), prepared by confined thin filmmelt (CTFMP) and solution (CTFSP) and bulk solution polymerization, were characterized by transmission electronmicroscopy, electron dimaction and molecular modeling. The unit cell is monoclinic (P21/a space group) with parameters a =7.89, b = 5.49, c = 12.65 A, α=γ= 90°, β=100.33°, density = 1.48 g/cm3, the a, b and β values differing slightly from thosereported previously in the literature. A degree of variation in relative intensities of hk0 reflections in,apparently,untilted [001] ED patterns was observed from a given sample,suggesting some variation in molecular packing.ED evidence was found for a second phase,with [001] appearing the same as for phase II of the related poly(p-oxybenzoate) (PpOBA) polymer.CTFMP crystals polymerized obove 220℃ (up to 370℃) and CTFSP crystals polymerized at 300℃ consisted of lamellae 100-200 A thick.
The morphology and crytal structure of poly(p-phenylene terephthalate) (PPT), prepared by confined thin filmmelt (CTFMP) and solution (CTFSP) and bulk solution polymerization, were characterized by transmission electronmicroscopy, electron dimaction and molecular modeling. The unit cell is monoclinic (P21/a space group) with parameters a =7.89, b = 5.49, c = 12.65 A, α=γ= 90°, β=100.33°, density = 1.48 g/cm3, the a, b and β values differing slightly from thosereported previously in the literature. A degree of variation in relative intensities of hk0 reflections in,apparently,untilted [001] ED patterns was observed from a given sample,suggesting some variation in molecular packing.ED evidence was found for a second phase,with [001] appearing the same as for phase II of the related poly(p-oxybenzoate) (PpOBA) polymer.CTFMP crystals polymerized obove 220℃ (up to 370℃) and CTFSP crystals polymerized at 300℃ consisted of lamellae 100-200 A thick.
2003, 21(2): 205-221
Abstract:
Confined thin film melt polymerization (CTFMP) of naphthalene chloride/hydroquinone (NCMQ, 1/1, molar)mixtures at polymerization temperatures (Tp) below ca. 300℃ resulted in relatively thick, elongated crystals. Polymerizationof NC/HQ above 300℃ between glass yielded well-formed lamellar crystals ca. 100 A thick. Phase Ⅰ and Ⅱ [001] EDpatterns were obtained for all Tp, the relative amount of phase Ⅰ increasing with Tp. Polymerization of naphthalenedicarboxylic acid/hydroquinione diacetate 1/1 mixtures at high Tp also yielded lamellar crystals that "curled up" off of the substrate.When the high temperature CTFMP polymerization was conducted between mica,aggregates of lamellae on-edge developed but epitaxial growth did not occur.Epitaxial growth of lamellae between mica could be obtained,however,by confined thin film solution polymerization,with both of the latter samples yielding apparently related ED patterns from a different unit cell than phase I or II.Fiber patterns,obtained from sheared samples,indicated considerably greater crystal disorder than in the nascent crystals.Refinement of the phase I unit cell parameters,based on the [001] and [011] ED patterns,with modeling based on Cerius2,suggests a monoclinic phase I unit cell with α=7.76,b=5.71,c=14.99A,α=γ=90°,β=99.7°,ρ=1.47 g/cm3,space group P121/a1.
Confined thin film melt polymerization (CTFMP) of naphthalene chloride/hydroquinone (NCMQ, 1/1, molar)mixtures at polymerization temperatures (Tp) below ca. 300℃ resulted in relatively thick, elongated crystals. Polymerizationof NC/HQ above 300℃ between glass yielded well-formed lamellar crystals ca. 100 A thick. Phase Ⅰ and Ⅱ [001] EDpatterns were obtained for all Tp, the relative amount of phase Ⅰ increasing with Tp. Polymerization of naphthalenedicarboxylic acid/hydroquinione diacetate 1/1 mixtures at high Tp also yielded lamellar crystals that "curled up" off of the substrate.When the high temperature CTFMP polymerization was conducted between mica,aggregates of lamellae on-edge developed but epitaxial growth did not occur.Epitaxial growth of lamellae between mica could be obtained,however,by confined thin film solution polymerization,with both of the latter samples yielding apparently related ED patterns from a different unit cell than phase I or II.Fiber patterns,obtained from sheared samples,indicated considerably greater crystal disorder than in the nascent crystals.Refinement of the phase I unit cell parameters,based on the [001] and [011] ED patterns,with modeling based on Cerius2,suggests a monoclinic phase I unit cell with α=7.76,b=5.71,c=14.99A,α=γ=90°,β=99.7°,ρ=1.47 g/cm3,space group P121/a1.
2003, 21(2): 223-230
Abstract:
We report on generating uniaxial negative birefringent compensation films, made of specifically designedpolyimides. These polymers were synthesized via a polycondensation of dianhydride [such as 2, 2' -bis(3, 4-dicarboxyphenyl)hexafluoropropane dianhydride] and 2, 2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl. The uniaxial negative birefringent (nx =ny > nz) polyimide substrates are achieved using a solution-casting method in conventional solvents, which exhibit the desirable optical phase retardation [(nx-nz)×d] values from 50 to 400 nm varying with the film thickness.In these polyimide films,the long chain rigid molecules adopt intrinsic planar orientation.In detail,the majority of phenylene-imide rings and phenylenes preferentially adopt nearly planar conformations parallel to the film substrate.In addition,these films also possess high transparency(or transmittance) and little color shift.The unique color dispersion curve indicates that this type of materials is very suitable for the applications in LCDs due to an excellent mimic for the retardation color dispersion curve with respect to LC molecules.Significantly low in-plane retardation(<1 nm) allows this new technology based film to achieve sufficiently high contrast ratio while highly negative retardation dramatically suppresses the gray scale inversion to improve the viewing angle performance in a variety of new mode LCDs.
We report on generating uniaxial negative birefringent compensation films, made of specifically designedpolyimides. These polymers were synthesized via a polycondensation of dianhydride [such as 2, 2' -bis(3, 4-dicarboxyphenyl)hexafluoropropane dianhydride] and 2, 2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl. The uniaxial negative birefringent (nx =ny > nz) polyimide substrates are achieved using a solution-casting method in conventional solvents, which exhibit the desirable optical phase retardation [(nx-nz)×d] values from 50 to 400 nm varying with the film thickness.In these polyimide films,the long chain rigid molecules adopt intrinsic planar orientation.In detail,the majority of phenylene-imide rings and phenylenes preferentially adopt nearly planar conformations parallel to the film substrate.In addition,these films also possess high transparency(or transmittance) and little color shift.The unique color dispersion curve indicates that this type of materials is very suitable for the applications in LCDs due to an excellent mimic for the retardation color dispersion curve with respect to LC molecules.Significantly low in-plane retardation(<1 nm) allows this new technology based film to achieve sufficiently high contrast ratio while highly negative retardation dramatically suppresses the gray scale inversion to improve the viewing angle performance in a variety of new mode LCDs.
2003, 21(2): 231-239
Abstract:
Short chain branching has been characterized using thermal fractionation, a stepwise isothermal crystallizationtechnique, followed by a melting analysis scan using differential scanning calorimetry. Short chain branching distributionwas also characterized by a continuous slow cooling crystallization, followed by a melting analysis scan. Four differentpolyethylenes were studied: Ziegler-Natta gas phase, Ziegler-Natta solution, metallocene, constrained-geometry single sitecatalyzed polyethylenes. The branching distribution was calculated from a calibration of branch content with melting temperature.The lamellar thickness was calculated based on the thermodynamic melting temperature of each polyethylene and the surface free energy of the crystal face.The branching distribution and lamellar thickness distribution were used to calculate weight average branch content,mean lamellar thickness,and a branch dispersity index.The results for the branch content were in good agreement with the known comonomer content of the polyethylenes.A limitation was that high branch content polyethylenes did not reach their potential crystallization at ambient temperatures.Cooling to sub-ambient was necessary to equilibrate the crystallization,but melting temperature versus branch content was not applicable after cooling to below ambient because the calibration data were not performed in this way.
Short chain branching has been characterized using thermal fractionation, a stepwise isothermal crystallizationtechnique, followed by a melting analysis scan using differential scanning calorimetry. Short chain branching distributionwas also characterized by a continuous slow cooling crystallization, followed by a melting analysis scan. Four differentpolyethylenes were studied: Ziegler-Natta gas phase, Ziegler-Natta solution, metallocene, constrained-geometry single sitecatalyzed polyethylenes. The branching distribution was calculated from a calibration of branch content with melting temperature.The lamellar thickness was calculated based on the thermodynamic melting temperature of each polyethylene and the surface free energy of the crystal face.The branching distribution and lamellar thickness distribution were used to calculate weight average branch content,mean lamellar thickness,and a branch dispersity index.The results for the branch content were in good agreement with the known comonomer content of the polyethylenes.A limitation was that high branch content polyethylenes did not reach their potential crystallization at ambient temperatures.Cooling to sub-ambient was necessary to equilibrate the crystallization,but melting temperature versus branch content was not applicable after cooling to below ambient because the calibration data were not performed in this way.
2003, 21(2): 241-249
Abstract:
In this paper we would like to give a brief review about the extensibility of the liquid-liquid locus into the negativepressure region. Negative pressure states are hardly explored; most researchers believe that the pressure scale ends at p = 0.We would like to show that this is not true, the p = 0 point is not a special point for liquids, it can be "easily" crossed. We aregoing to give a few example, where the extension of liquid-liquid locus for polymer blends and solutions below p = 0 gives us some interesting results,like the merging of UCST and LCST branches in weakly interacting polymer solutions of the reason why most UCST blends exhibit pressure induced immiscibility.Also we will see what happens with the immiscibility island of aqueous polymer solutions when—reaching the critical molar mass—it"disappears".
In this paper we would like to give a brief review about the extensibility of the liquid-liquid locus into the negativepressure region. Negative pressure states are hardly explored; most researchers believe that the pressure scale ends at p = 0.We would like to show that this is not true, the p = 0 point is not a special point for liquids, it can be "easily" crossed. We aregoing to give a few example, where the extension of liquid-liquid locus for polymer blends and solutions below p = 0 gives us some interesting results,like the merging of UCST and LCST branches in weakly interacting polymer solutions of the reason why most UCST blends exhibit pressure induced immiscibility.Also we will see what happens with the immiscibility island of aqueous polymer solutions when—reaching the critical molar mass—it"disappears".
