Polyacrylate formation

Drivers for Performing Polyacrylate Formation in Micro Reactors... 

Beneficial Micro Reactor Properties for Polyacrylate Formation... 

Polyacrylate Formation Investigated in Micro Reactors Organic synthesis 61 [OS 61] Radical polymerization of acrylates... 

Figure 4.73 Schematic of laboratory-scale experimental set-up for polyacrylate formation. The Sulzer-type pre-mixer can be replaced by an interdigital micro mixer [125].

Sun F, Castner D G and Grainger D W Ultrathin 1993 Self-assembled polymeric films on solid-surfaces. 2. Formation of 11-(n-pentyldithio)undecanoate-bearing polyacrylate monolayers on gold Langmuirs 3200-7... 

In the same year, Fulda and Tieke [75] reported on Langmuir films of monodisperse, 0.5-pm spherical polymer particles with hydrophobic polystyrene cores and hydrophilic shells containing polyacrylic acid or polyacrylamide. Measurement of ir-A curves and scanning electron microscopy (SEM) were used to determine the structure of the monolayers. In subsequent work, Fulda et al. [76] studied a variety of particles with different hydrophilic shells for their ability to form Langmuir films. Fulda and Tieke [77] investigated the influence of subphase conditions (pH, ionic strength) on monolayer formation of cationic and anionic particles as well as the structure of films made from bidisperse mixtures of anionic latex particles. 

For the characterization of Langmuir films, Fulda and coworkers [75-77] used anionic and cationic core-shell particles prepared by emulsifier-free emulsion polymerization. These particles have several advantages over those used in early publications First, the particles do not contain any stabihzer or emulsifier, which is eventually desorbed upon spreading and disturbs the formation of a particle monolayer at the air-water interface. Second, the preparation is a one-step process leading directly to monodisperse particles 0.2-0.5 jim in diameter. Third, the nature of the shell can be easily varied by using different hydrophilic comonomers. In Table 1, the particles and their characteristic properties are hsted. Most of the studies were carried out using anionic particles with polystyrene as core material and polyacrylic acid in the shell. 

Nicholson, J. W., Brookman, P. J., Lacy, O. M., Sayers, G. S. Wilson, A. D. (1988a). A study of the nature and formation of zinc polyacrylate cement using Fourier transform infrared spectroscopy. Journal of Biomedical Materials Research, 22, 623-31. 

The precise nature of the adhesion of the polyelectrolyte cements to untreated dental enamel and dentine has yet to be established. The earliest theory was due to Smith (1968) who speculated that the polyacrylate chains of the cement formed a chelate with calcium ions contained in the hydroxyapatite-like mineral in enamel and dentine. Beech (1973) considered this unhkely since it involved the formation of an eight-membered ring. Beech studied the interaction between PAA and hydroxyapatite, identified the formation of polyacrylate and so considered that adsorption was due to ionic attraction. 

He compared the infrared spectra of cements with that of zinc polyacrylate salt and found differences. Inspection of his data shows that, unlike the cements, the salt was purely ionic, so that it seems here that cement formation is associated with the formation of coordination complexes. There are no ligand field stabilization effects with the Zn ion because it has a completed d shell (Cotton Wilkinson, 1966). For this reason the... 

Figure 5.11 (Crisp Wilson, 1974b) shows the time-dependent variation of the concentration of soluble ions in setting and hardening cements. Note that the concentrations of aluminium, calcium and fluoride rise to maxima as they are released from the glass. After the maximum is reached the concentration of soluble ions decreases as they are precipitated. Note that this process is much more rapid for calcium than for aluminium and the sharp decline in soluble calcium corresponds to gelation. This indication is supported by information from infrared spectroscopy which showed that gelation (initial set) was caused by the precipitation of calcium polyacrylate. This finding was later confirmed by Nicholson et al. (1988b) who, using Fourier transform infrared spectroscopy (FTIR), found that calcium polyacrylate could be detected in the cement paste within one minute of mixing the cement. There was no evidence for the formation of any aluminium polyacrylate within nine minutes and substantial amounts are not formed for about one hour (Crisp et al, 1974).

Polyacrylates are often added to drilling fluids to increase viscosity and limit formation damage. The filter-cake is critical in preventing reservoir invasion by mud filtrate. Polymer invasion of the reservoir has been shown to have a great impact on permeability reduction [98]. The invasion of filtrate and solids in drilling in fluid can cause serious reservoir damage. 

Attapulgite adsorbs excess fluid in the stool with few adverse effects. Calcium polycarbophil is a hydrophilic polyacrylic resin that also works as an adsorbent, binding about 60 times its weight in water and leading to the formation of a gel that enhances stool formation. Neither attapulgite nor polycarbophil is systemically absorbed. Both products are effective in reducing fluid in the stool but can also adsorb nutrients and other medications. Their administration should be separated from other oral medications by 2 to 3 hours. Psyllium and methylcellulose products may also be used to reduce fluid in the stool and relieve chronic diarrhea. 

Table I demonstrates that most liquid crystalline polymers lacking a spacer are formed from a flexible polyacrylate backbone. In contrast, the methyl substituent in polymethacrylate backbones both reduce main chain mobility and imposes additional steric barriers to mesophase formation. Therefore, successful liquid crystalline formation of polymethacrylates has been achieved only...

Scale inhibitors are used to prevent the formation of insoluble calcium salts when the drilling fluid contacts formation minerals and saline formation waters. Commonly used scale inhibitors include sodium hydroxide, sodium carbonate, sodium bicarbonate, polyacrylates, polyphosphates, and phosphonates. 

Thus, polymethacrylic acid undergoes net scission on gamma radiolysis with a G-value of approximately 4, while polyacrylic acid, on the other hand, undergoes net crosslinking with a G-value of approximately 1.2 (7). Crosslinking in polyacrylic acid is favourable because of the formation of main chain radicals. These can react to form crosslinks between polymer chains. 

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