Diblock hybrids

DIBLOCK HYBRIDS PREPARED BY POLYMERIZATION FROM A DENDRITIC INITIATOR... 

Covalently connecting two incompatible polymers at their ends leads to a fascinating class of self-assembling materials [1]. Block copolymers constitute a well-studied and well-documented set of nanostructured hybrid materials [2], Many synthetic techniques are available for generating AB diblock, ABA triblock, ABC triblock and even more complicated block architectures [3,4], Furthermore, the thermodynamics governing the self-assembly... 

Regardless of the desired architecture, there are three main synthetic approaches to the preparation of diblock, dumbbell or dendronized hybrid copolymers. These involve grafting, polymerization or stepwise dendritic growth... 

The properties of the hybrid diblock structures can be altered drastically by simply taking advantage of the high terminal functionality of the dendritic block. For example unusual diblock structures useful for the modification of surfaces have been prepared by ATRP of polystyrene (PS) initiated from the benzylic halide focal point of Frechet-type dendrons with terminal isophthalate ester groups [9b], Well-defined copolymers with narrow molecular weight distributions were obtained and excellent agreement was observed between calculated... 

In order to explore the properties that may be obtained by hybridizing the linear and dendritic architectural states, both diblock and triblock copolymer... 

To take a closer look at the area per molecule in the condensed phase of the diblock monolayers, the x-axis of Fig. 4.14a is expanded and shown in Fig. 4.14c. The extrapolated value of the area per molecule and the theoretically expected value for the area are listed in Table 4.5. To calculate the theoretically expected area for the hybrid block copolymers in the condensed phase, it is assumed that the stearate end groups are extended into the air perpendicular to the air-water interface as shown schematically in Fig. 4.14d. This assumption is based on the behavior of pure stearic acid, which forms ordered monolayers with the alkyl chains oriented perpendicular to the air-water interface. The area per molecule for stearic acid with this orientation is 20 A2, [113] Here, the theoretically expected area was calculated by multiplying the area per stearate molecule (20 A2) with the number of stearate groups present at the ends of the dendrimer block. PEO(2k)-S having no dendrimer block but a single... 

Table 1 Examples of polypeptide hybrid block copolymers prepared from macromolecular amine initiators [8,9]. Block architectures are primarily AB diblocks or ABA triblocks, where the polypeptide segment is the A domain, and the macroinitiator is the B domain ...

Fig. 7 Phase diagrams describing the solid-state nanoscale structure of A PS-PBLG and B PS-PZLL diblock copolymers C Illustration of the lamellar, double hexagonal and hexagonal morphologies found for the low molecular weight hybrid block copolymers...

One of the first studies focussing on the sohd-state properties of peptide-polyester synthetic hybrid block copolymers was reported by Jerome etal. [71]. DSC experiments on a poly(e-caprolactone)5o-b-poly(y-benzyl-L-glutamate)4o (PCL50-PBLG40) diblock copolymer revealed two endotherms. 

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