Copolymerization hydrophobic monomer

We applied CDs to solubilize various types of vinyl monomers which are otherwise water insoluble. This unique behaviour of CD allows it to copolymerize hydrophobic monomers complexed in CDs with water soluble comonomers. 

Another way for covalent immobilisation is to synthesise indicator chemistry with polymerizable entities such as methacrylate groups (Figure 4). These groups can then be copolymerized with monomers such as hydrophobic methyl methacrylate or hydrophilic acryl amide to give sensor copolymers. In order to obtain self-plasticized materials, methacrylate monomers with long alkyl chains (hexyl or dodecyl methacrylate) can be used. Thus, sensor copolymers are obtained which have a Tg below room temperature. Similarly, ionophores and ionic additives (quaternary ammonium ions and borates) can be derivatised to give methacrylate derivatives. 

In the conventional emulsion polymerization, a hydrophobic monomer is emulsified in water and polymerization initiated with a water-soluble initiator. Emulson polymerization can also be carried out as an inverse emulsion polymerization [Poehlein, 1986]. Here, an aqueous solution of a hydrophilic monomer is emulsified in a nonpolar organic solvent such as xylene or paraffin and polymerization initiated with an oil-soluble initiator. The two types of emulsion polymerizations are referred to as oil-in-water (o/w) and water-in-oil (w/o) emulsions, respectively. Inverse emulsion polymerization is used in various commerical polymerizations and copolymerizations of acrylamide as well as other water-soluble monomers. The end use of the reverse latices often involves their addition to water at the point of application. The polymer dissolves readily in water, and the aqueous solution is used in applications such as secondary oil recovery and flocculation (clarification of wastewater, metal recovery). 

Emulsifier-free latices are useful not only for industrial purposes but also for studies on colloidal properties (1, 2) and medical applications (3, h). Various methods have been tried to prepare characteristic emulsifier-free latices (5-8). Among them, copolymerization of hydrophobic monomers with hydrophilic comonomers has been the most applicable one (7, 8). There have been many studies on the effects of ionic comonomers on the kinetics of aqueous copolymerization and the properties of the resulting latices, but nonionic hydrophilic comonomers have rarely been used for these purposes. 

The First Stage. The preferential polymerization of AA at the initial stage of copolymerization means that the main reaction locus is the aqueous phase just as Juang and Krieger pointed it out for the aqueous copolymerization of St with sodium styrenesul-fonate ( SSS ) (9). In the St-SSS system, SSS polymerized preferentially up to a few percent conversion under the condition of SSS/St (w/w) - 0.014. Copolymerization of hydrophobic monomer with a large amount of hydrophilic comonomer was considered to yield a greater amount of information with respect to the reaction mode. By use of a relatively large amount of AA or its derivatives the characteristic reaction mode of the copolymerization of St with acrylamides could be clarified. 

Amphiphilic graft copolymers are conveniently synthesized by copolymerization of a hydrophobic monomer with a hydrophilic macromonomer and vice versa. The resulting copolymers are of great interest from the point of view of their surface active properties. 

The copolymerization of monomers where one of the monomers acts as the hydrophobe was reported by Reimers and Schork [26]. MMA was copolymerized with p-methylstyrene, vinyl hexanoate, or vinyl 2-ethylhexanoate. The resulting copolymer composition tended to follow the predictions of the reactivity ratios, i.e., the reaction progresses as a bulk reaction. In contrast, copolymer compositions obtained from the (macro)emulsion copolymerizations tended to be more influenced by the relative water solubility of the comonomer and mass transfer. Wu and Schork used monomer combinations with large differences in reactivity ratios and water solubility vinyl acetate/butyl acrylate,... 

As the water solubility of the comonomer decreases, the difference in incorporation of the hydrophobic monomer between the mini- and macroemulsion polymerization becomes more pronounced. This was seen in the copolymerization of VH/MMA. The fraction of the hexanoate in the copolymer formed in the miniemulsion polymerization was substantially higher than that found with the macroemulsion. This incorporation closely follows the copolymer equation. The VEH/MMA miniemulsion copolymerization also followed the copolymer equation. Differences between the mini- and macroemulsion polymerization are not as pronounced in this system. For the VD/MMA and VS/MMA systems there were large differences between the two copolymerizations. In addition, none of the mini- or macroemulsion copolymerizations of vinyl decanoate or vinyl stearate are predicted by the copolymer equation. The miniemulsion copolymerizations fall above the prediction curve (more hydrophobic monomer incorporation than predicted), and the macroemulsions fall below. In these cases, both micellar and droplet nucleation took place in the miniemulsion polymerizations, and the presence of micelles tended to enrich the concentration of the hydrophobic monomer in the droplets, since the micelles would likely be richer in the more water-soluble MMA. 

Extremely hydrophobic monomers do not polymerize well via macroemulsion polymerization due to their very low rates of monomer transport across the aqueous phase. Obviously, these monomers can be polymerized much more effectively in a miniemulsion system. One example of this is provided by Landfester et al. [320]. In this paper,fluoroalkyl acrylates are polymerized in a miniemulsion with low levels of a protonated surfactant. When fluorinated monomers were copolymerized with standard hydrophobic and hydrophilic monomers, either core-shell structures or statistical copolymers were formed. 

The copolymerization of species having hydrophilic side groups with hydrophobic monomer units has led to the development of water-dispersible coatings of considerable promise. The morphology of these polymers and the orientation that takes place at the interface are of particular importance, for organic cosolvents are used in the copolymer synthesis and also as solubilizers. 

Starved-feed emulsion polymerization can be conducted without emulsifiers if suitable comonomers and procedures are utilized.341 Polymerization of a water-soluble methacrylate like HEMA in the presence of a CCT agent is carried out initially. The resulting HEMA oligomer is further copolymerized with hydrophobic monomers so that the resulting diblock copolymer serves as a surfactant (see, for instance, sections 5.3 and 5.4). During the cross-linking process, all of this surfactant is incorporated into the polymer backbone and is thus immobilized, overcoming the problem of residual surfactant in the final product. 

In the proceeding sections, emphasis has been placed on pH-responsive homopolymers whose conformational behavior is dictated by the hydrophobic to hydrophilic balance within the system. The switch in conformation is marked by a change in macroscopic properties, such as solution viscosity, over a narrow and characteristic pH range specific to that polymer which is important from a technological viewpoint. Manipulation of the switch to any desired pH has attracted much interest in the literature because this could lead to many more potential applications for the modified poly electrolyte. Synthetic strategies adopted to achieve this end have included simple copolymerization of an ionizable repeat unit with a hydrophobic monomer [20,27—43,1291 to form statistical copolymers and formation of block copolymers [71,158-180]. (A block copolymer consists of sequences of monomers A and B such as -(A) -(B)m or -(A) -(B)m-(A) , where n and m represent the number of repeat units.)... 

Radical termination. Normal termination reactions would be expected to take place in the continuous phase. These reactions will not be the dominant method of radical termination, but water-phase termination can be quite important if water-soluble monomers are used. Water-soluble polymer can be formed with such monomers even though most of the monomer will copolymerize with the hydrophobic monomer in the particles. 

Copolymerization. Synthetic HMWSPs can be prepared according to this approach by the copolymerization of a vinyl or epoxide monomer (4) with a small amount of a specific hydrophobic monomer that is copolymer-izable with the primary monomer as shown in Scheme II. The hydrophobe content of the polymers can be tailored by controlling the amount of the hydrophobic comonomer used in the polymerization process. The nature of the group (i.e., ether, ester, carbamate, etc.) connecting the long-chain... 

Novel polymerization techniques were used to synthesize new macro-molecules that consisted of a water-soluble backbone unth small amounts of hydrophobic functionality. Micellar polymerization is based on the capability of surfactant micelles to solubilize hydro-phobic molecules into an aqueous medium it was used to copolymerize acrylamide and hydrophohically substituted acrylamide monomers. A critical aspect of these polymerizations was the incorporation of the hydrophobic monomer into the water-soluble polymers. A method that used the UV chromophore of newly synthesized N-aryl substituted acrylamides was developed to quantify incorporation at the low levels of hydrophobe normally used about 1 mol %). The synthesis of the substituted acrylamides, the UV technique, and results obtained with it are discussed. 

On further examination, over half of the AST patents listed were classified as associative in this review. Although most of these occur in more recent years, the earliest found (59) happens to be the first entry in the tables. In this and four other former issues (62, 64, 69, 70) that differ in the type of hydrophobic monomer employed, a maleic-anhydride-con-taining prepolymer is prepared and subsequently post-esterified with a nonionic surfactant. In essence, the associative side chains are grafted onto the polymer backbone. In nearly all of the other associative patents, the associative monomers are synthesized first and then copolymerized with the carboxylic acid and hydrophobic monomers. Many similarities also exist between the various associative AST patents. In refs. 62, 64, 69, and 70, the hydrophobic monomer was an obvious variable. In some others, differentiation is a manifestation of the type of coupling agent used. 

These can be made by copolymerizing two monomers, one of which contains a side-chain such as Cio or C12, e.g. the copolymerization of norbomene dicarboxylic esters with 5-decylnorbom-2-ene. Alternatively, the homopolymer of the diester can first be hydrolyzed to the acid form and then partially reacted with 1-dodecylamine. The viscosity of aqueous solutions of such hydrophobically modified polymers increases sharply with increase in concentration as a result of intermolecular association (McArdle 1995). 

SUG Sngihara, S., Kanaoka, S., and Aoshima, S., Thermosensitive random copolymers of hydrophilic and hydrophobic monomers obtained by living cationic copolymerization, Macrowzo/ecw/ra, 37, 1711, 2004. 

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