Calixarene-functionalized polymers

For other applications such as in electrokinetics or the synthesis of radiopharmaceuticals it is desirable that the calixarene-functionalized polymer be soluble in aqueous media. In order to achieve such a goal it is necessary to avoid the formation of cross-linking within the polymer. Such a polymer 12 that is soluble in aqueous or organic solvents is formed when a calixarene with a single haloalkyl substituent on the upper rim is reacted with the polyethyleneimine solution (Equation 9). 

Gabriel Rokicki is a chemistry professor at the Faculty of Chemistry, Warsaw University of Technology, Poland, where he received all his academic education (MSc in 1971, PhD in 1989, and tenure professor in 2002). His current scientific activities include synthesis, stmcture, and properties of polymer materials, such as aliphatic polycarbonates, polyurethanes, epoxy resins, and biodegradable polymers. He has devoted a special interest to the use of functional polymers in obtaining specialty ceramic materials as well as to polymer recycling. Earlier major interests included the utilization of carbon dioxide and cyclic carbonates in the synthesis of condensation polymers. Another topic of interest was polymeric ion-sensors based on modified calixarenes. He is the author and coauthor of 160 scientific papers and holds more than 50 patents in the above-mentioned areas. At the Faculty of Chemistry of Warsaw University of Technology, he conducts lectures on polymer chemistry and technology. 

In principle, there are four basic strategies to compensate for the repulsive effects between the hydrophobic fullerene surface and water (a) encapsulation in the internal hydrophobic moiety of water-soluble hosts like cyclodextrins (Andersson et al., 1992 Murthy and Geckeler, 2001), calixarenes (Kunsagi-Mate et al., 2004) or cyclotriveratrylenes (Rio and Nierengarten, 2002) (b) supramolecular or covalent incorporation of fullerenes or derivatives into water-soluble polymers (Giacalone and Martin, 2006) or biomolecules like proteins (Pellarini et al., 2001 Yang et al., 2007) (c) suspension with the aid of appropriate surfactants and (d) direct exohe-dral functionalization in order to introduce hydrophilic moieties. 

The star polymers obtained with the bromoester-type calixarene-based initiators were analyzed by SEC equipped with a multiangle laser light scattering (MALLS) detector. The arm numbers were well controlled (close to the initiator s functionality), although the octafunctional initiator MI-51 induced star—star coupling in the styrene-polymerization at conversions higher than 20%.421 A similar series of tetra-, hexa-, and octafunctionalized initiators with calixarene cores were synthesized for sulfonyl chloride versions (MI-41, MI-48, and MI-52) and employed for copper-catalyzed MMA polymerizations.343... 

The first step for the core-first stars is the synthesis of multifunctional initiators. Since it is difficult to prepare initiators that tolerate the conditions of ionic polymerization, mostly the initiators are designed for controlled radical polymerization. Calixarenes [39, 58-61], sugars (glucose, saccharose, or cyclodextrins) [62-68], and silsesquioxane NPs [28, 69] have been employed as cores for various star polymers. For the growth of the arms, mostly controlled radical polymerizations were used. There are only very rare cases of stars made from nitroxide-mediated radical polymerization (NMRP) [70] or reversible addition-fragmentation chain transfer (RAFT) techniques [71,72], In the RAFT technique one has to differentiate between approaches where the chain transfer agent is attached by its R- or Z-function. ATRP is the most frequently used technique to build various star polymers [27, 28],... 

Functional calixarenes can be used as plurifunctional ATRP initiators for the synthesis of star polymers. Show the structures of 2-bromopropionate and 2-bromoisobutyrate esters of 4-ten-butyl calix[ ] arene used as tetrafunctional ( = 4), hexafunctional (h = 6), and octafunctional (n = 8) initiators for ATRP. 

Polycaps based on H-bonded calixarene units functionalized with urea and hosting a small guest molecule were also reported. Isotropic solutions in o-dichlorobenzene revealed polymer like properties, notably strong normal forces supporting the permanence of a significant DP even under a flow fleld [112]. 

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