Poly cloud point temperatures

Suzuki et al. reported cloud-point temperatures as a function of pressure and composition in mixtures of poly(ethyl acrylate) and poly(vinylidene fluoride) [9], Their data in terms of p(T) curves at constant composition show that miscibility in the same system may either improve or decline with rising pressure, depending on the blend s composition. Important consequences for blend-processing ensue. A planned two-phase extrusion may easily be jeopardized by the pressure building up in the extruder. Conversely, a homogeneous melt may be turned into a two-phase system when the pressure on the blend increases. 

EOS models were derived for polymer blends that gave the first evidence of the severe pressure - dependence of the phase behaviour of such blends [41,42], First, experimental data under pressure were presented for the mixture of poly(ethyl acetate) and polyfvinylidene fluoride) [9], and later for in several other systems [27,43,44,45], However, the direction of the shift in cloud-point temperature with pressure proved to be system-dependent. In addition, the phase behaviour of mixtures containing random copolymers strongly depends on the exact chemical composition of both copolymers. In the production of reactor blends or copolymers a small variation of the reactor feed or process variables, such as temperature and pressure, may lead to demixing of the copolymer solution (or the blend) in the reactor. Fig. 9.7-1 shows some data collected in a laser-light-scattering autoclave on the blend PMMA/SAN [46],... 

Figure 30.1 The cloud point temperature of poly(propargyl glycolide) grafted with varying amounts of oligoethylene glycol and 1-decyl azide as measured using UV-visible spectrometry at a wavelength of 450 nm. Reproduced with permission from Ref. [82] 2008, American Chemical Society.

Cloud point temperature (CP, determined at 1 K min- ) and coexistence ( determined by refractive index of the low and high polymer concentration phases after 24 h equilibration) curves obtained for a binary mixture of a comb-shaped poly[oligo(2-ethyl-2-oxazoline) methacrylate] in water.The coexistence curve is fitted to guide the eye (Weber et al., 2013). (Source-. Reprinted with permission from Wiley.)... 

Variation of cloud point temperature (Tcp)of poly(oligo ethylene glycol methacrylate)s (POEGMA)s as a function of the number of oligo(ethylene oxide) units (m) and end-group functionality (Ishizone etal., 2008). (Source-. Reprinted with permission from ACS.)... 

A2 (a) Structure and cloud point temperatures (7cp) of common poly(betaine)s. (b) Phase diagram for the UCST behavior of poly(2-dimethyl(methacryloxyethyl) ammonium propane sulfonate) (PDMAPS-MA) in water as a function of the degree of polymerization (Nspe) (Mary eta ., 2007). Source Reprinted with permission from the ACS.)... 

PPE poly(phenylene ether) T c ceiling temperature cloud-point temperature... 

Linear alkane solutions of 60a (n = 300, M = 3.1 x 10", Mw/Mn = 1.15) showed highly sensitive UCST-type phase separation irrespective of the solvent [222]. Interestingly, the cloud point temperature of 60a increased linearly with the number of carbon atoms in the alkane, which is in reasonable agreement with the Flory-Huggins theory. Similar phase separation occurred for poly(vinyl ether)s with various pendant groups, such as alkyl (in alcohols and esters), ester (in alcohols and toluene), and silyloxy groups (in alcohols). The combination of polymer and solvent was the decisive factor in sensitive phase separation. Nonpolar polymers underwent phase separation in polar solvent, and polar ones became thermosensitive in nonpolar media. 

The temperature-driven self-assembly of nonionie amphiphilie tailor-made triblock copolymers was studied by DLS, NMR, ITC, and SAXS. The composition of these triblock copolymers is more complex than that of the vast majority of poly(2-allqrl-2-oxazoline)s a statistical thermo-responsive (iPrOx) and hydrophobic (BuOx) central block with terminal hydrophilic blocks (MeOx). Researchers made a first attempt to resolve the effects of each block on nanoparticle formation. The iPrOx/MeOx ratio dets. the value of the cloud point temperature, whereas the different BuOx-iPrOx blocks determine the character of the process. Finally, a study on the thermodynamic and structural profiles of the complexation between these triblock poly(2-allqrl-2-oxazoline)s and two ionic surfactants was presented. 

Tempera.ture Effect. Near the boiling point of water, the solubiUty—temperature relationship undergoes an abmpt inversion. Over a narrow temperature range, solutions become cloudy and the polymer precipitates the polymer caimot dissolve in water above this precipitation temperature. In Figure 4, this limit or cloud point is shown as a function of polymer concentration for poly(ethylene oxide) of 2 x 10 molecular weight. 

Solubility. Poly(vinyl alcohol) is only soluble in highly polar solvents, such as water, dimethyl sulfoxide, acetamide, glycols, and dimethylformamide. The solubiUty in water is a function of degree of polymerization (DP) and hydrolysis (Fig. 4). Fully hydrolyzed poly(vinyl alcohol) is only completely soluble in hot to boiling water. However, once in solution, it remains soluble even at room temperature. Partially hydrolyzed grades are soluble at room temperature, although grades with a hydrolysis of 70—80% are only soluble at water temperatures of 10—40°C. Above 40°C, the solution first becomes cloudy (cloud point), followed by precipitation of poly(vinyl alcohol). 

In most cases, these active defoaming components are insoluble in the defoamer formulation as weU as in the foaming media, but there are cases which function by the inverted cloud-point mechanism (3). These products are soluble at low temperature and precipitate when the temperature is raised. When precipitated, these defoamer—surfactants function as defoamers when dissolved, they may act as foam stabilizers. Examples of this type are the block polymers of poly(ethylene oxide) and poly(propylene oxide) and other low HLB (hydrophilic—lipophilic balance) nonionic surfactants. 

Guner A. and Kara M. Cloud points and temperatures of aqueous poly(N-vinyl-2-pyrrolidone) solutions in the presence of denaturing agents. Polymer 39, 8 9, 1569-1572,1998. 

An interesting family of polymeric ligands show inverse temperature dependence of solubihty in water, i.e. they can be precipitated from aqueous solutions by increasing the temperature above the so-called cloud point. Typically these ligands contain poly(oxyalkylene) chains, but the phenomenon can be similarly observed with poly(N-isopropyl acrylamide) derivatives (e.g. 132) and methylated cyclodextrins, too. At or above their cloud points these compounds fall off the solution, due to the break-up and loss of the hydration shell which prevents aggregation and precipitation of their molecules. Conversely, upon cooling below this temperature (also called the lower critical solution temperature, LCST) these substances dissolve again. 

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