Star-shaped copolymer

In a different approach, Hedrick et al. have studied multifunctional dendritic initiators for the synthesis of multiarm star-shaped copolymers [102]. Several dendritic initiators with hydroxyl functionality ranging from 2 to 48 have been prepared according to the method developed by Hult et al. [120]. The bulk polymerization of sCL initiated by these multifunctional macroinitiators and acti-... 

Interestingly, Hedrick and coworkers reported a metal-free approach for the synthesis of star-shaped copolymers. They synthesized star-shaped PCLs by the ROP of eCL initiated by polyols in the presence of unencumbered N-heterocyclic carbenes [87]. 

Figure 7 compares the water/toluene interfacial tensions measured in the presence of various commercial surfactants and P0/PS based diblock (8) and star-shaped copolymers the higher activity of the star-shaped block copolymers over a broad range of concentrations is clearly put in evidence. 

TABLE VII Toluene/Water Interfacial Tension of Diblock and Star-shaped Copolymers at Different Concentrations (20°C)... 

QuasicrystaUine phases form at compositions close to the related crystalline phases. When solidified, the resultant strucmre has icosahedra threaded by a network of wedge disclinations, having resisted reconstruction into crystalline units with three-dimensional translational periodicity. The most well-known examples of quasicrystals are inorganic phases from the ternary intermetallic systems Al-Li-Cu, Al-Pd-Mn, Zn-Mg-Ln, Al-Ni-Co, Al-Cu-Co, and Al-Mn-Pd. In 2007, certain blends of polyisoprene, polystyrene, and poly(2-vinylpyridine) were found to form star-shaped copolymers that assemble into the first known organic quasicrystals (Hayashida et al., 2007). 

Synthesis of star-shaped copolymers by the arm-first method.. 865... 

Two general strategies are possible for the synthesis of star-shaped copolymers The arm-first method is based on the reaction of living chains with plurifunctional electrophiles carrying at least three reacting groups alternatively, polymerization can be initiated by a multifunctional initiator according to the core-first method. 

The present volume is particularly concerned with the use of the different modes of controlled radical polymerisation for the preparation of copolymers such as random copolymers, linear block copolymers, as well as graft copolymers and star-shaped copolymers. It also presents the combination of controlled radical polymerisation with non-controlled radical copolymerisation, cationic and anionic polymerisation,both of vinyl monomers and cyclic monomers, and ringopening metathesis polymerisation. 

Smeets and co-workers reported the synthesis of amphiphilic HBP from the copolymerisation of a vinyl and divinyl monomers [11]. Grafting of HBP has also been reported by other researchers [12]. Hou and Yan reported the synthesis of a star-shaped copolymer using in situ grafting, which contained a hyperbranched poly(3-methyl-3-oxetanemethanol) core and tetrahydrofuran arms [13]. 

The examples presented above are limited in the intermolecular multi-component systems. For polymers, there are even many intramolecular multi-component systems, such as diblock copolymers with one end containing different chemical species than the other end, grafted copolymer, star-shape copolymers, and statistical copolymers. Complex self-assembly process of these copolymers can form hierarchical structures with certain flexibility in their envirmunental responses. It is not difficult to find such examples in the bio-functional macromolecular systems. 

Precision synthesis of microstructures in star-shaped copolymers of 8-caprolactone, LLA, and DXO was accomplished using a spirocyclic tin initiator and stannous(II) octoate (cocatalyst) together with pentaerythritol ethoxylate (coinitiator) [109]. 

Fujimoto, T., Zhang, H., Kazama, T., Isono, Y., Hasegawa, H. and Hashimoto, T. (1992) Preparation and characterization of novel star-shaped copolymers having 3 different branches. PoZymer, 33,2208-2213. 

Figure 4.2 Macromolecular topologies of amphiphilic polymers capable of forming self-assembled networks (a) linear block copolymers, (b) star-shaped copolymers, (c) graft copolymers.

Zhang,H.,Yan,Q.,Kang,Y.,Zhou,L.,Zhou,H.,Yuan,J. and Wu,S. (2012). Fabrication of thermo-responsive hydrogels from star-shaped copolymer with a biocompatible j3-cyclodextrin core. Polymer, 53,3719-3725. 

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