Multifunctional core-shell polymeric

Figure 6.11 Preparation of multifunctional core-shell polymeric nanoparticles from poly (NBE-indo)35-fa-(NBE-HEG),5. (Reprinted from Ref. [76].)...

There is a wide range of morphologies and compositions of polymeric microspheres. Core-shell microbeads can be created by sequentially polymerizing vinyl monomers, typically methacrylates and styrene. Each layer may consist of a homopolymer or a copolymer in the copolymers multifunctional vinyl monomers (e.g., diacrylates and divinylbenzene) may be used to create a cross-linked material. An optional final step can be grafting of functional groups to the surface in order to enhance compatibility to the surrounding medium. 

Block copolymers between alkyl acrylates such as B-4,358 B-5,202,203 and B-6,203 on the other hand, have been synthesized by the macroinitiator methods mostly with copper catalysts. Star block copolymers with a soft poly(MA) core and a hard poly(isobomyl acrylate) shell were synthesized by using multifunctional initiators.358 Poly(tBA) segments in B-5 and B-6 can be converted into hydrophilic poly(acrylic acid).203 Block copolymers between />methylstyrene and styrene (B-7) were also prepared by the rhenium-catalyzed living radical polymerization in conjunction with an alkyl iodide initiator.169... 

Figure 5 illustrates the type of encapsulation process, shown in Figure 4a, when the core material is a water-immiscible liquid. Reactant X, a multifunctional acid chloride, isocyanate, or a combination of these reactants, is dissolved in the core material. The resulting mixture is emulsified in an aqueous phase that contains an emulsifier such as partially hydrolyzed poly(vinyl alcohol) or a hgno-suMbnate. Reactant Y, a multifunctional amine or a combination of amines such as ethylenediamine, hexamethylenediamine, or triethylenetetramine, is added to the aqueous phase, thereby initiating interfacial polymerization and formation of a capsule shell. If reactant X is an acid chloride, a base is added to the aqueous phase in order to act as an acid scavenger. 

Wooley and coworkers utilized click chemistry to prepare block copolymer micelles and shell cross-linked nanoparticles (SCKs) presenting click-reactive functional groups on their surfaces [144,145]. Moreover, they presented the preparation of well-defined core cross-linked polymeric nanoparticles, utilizing multifunctional dendritic cross-linkers that allow for the effective stabilization of supramolecular polymer assemblies and the simultaneous introduction of reactive groups within the core domain [146]. 

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