Triarm star block copolymers

Lambert, O., Reutenauer, S., Hurtrez, G., Riess, G. and Dumas, P. (1998) Synthesis of amphiphUic triarm star block copolymers. Polym. Bull, 40, 143-149. 

Block Crystallization in Model Triarm Star Block Copolymers with Two Crystallizable Blocks ... 

Figure 2. SAXS (left) and WAXD (right ) spectra for the SEL-4.7/20/87 triarm star block copolymer taken at increments of 60 s following a T-jump from 383 to 313 K. The WAXD pattern after about 400 s shows peaks corresponding to the (110) and (200) reflections from the orthorhombic unit cell of PCL At the same time a SAXS peak develops characteristic of the PCL crystals. The SAXS invariant and the intensity of the most intense WAXD reflections are compared.

Nasser-Eddine, M., Reutenauer, S., Delaite, C. et al. (2004) Synthesis of polystyrene-poly(tert-butyl methacrylate)-poly(ethylene oxide) triarm star block copolymers. Journal of Polymer Science Part A-Polymer Chemistry, 42,1745-1751. 

By the use of the polymer-linking method with 20a, a variety of starshaped poly(vinyl ethers) have been synthesized (Scheme 12) [208-212]. A focus of these syntheses is to introduce polar functional groups, such as hydroxyl and carboxyl, into the multiarmed architectures. These functionalized star polymers include star block (23a,23b) [209,210], heteroarm (24) [211], and core-functionalized (25) [212] star polymers. Scheme 12 also shows the route for the amphiphilic star block polymers (23b) where each arm consists of an AB-block copolymer of 1BVE and HOVE [209] or a vinyl ether with a pendant carboxyl group [210], Thus, this is an expanded version of triarmed and tetraarmed amphiphilic block copolymers obtained by the multifunctional initiation (Section VI.B.2) and the multifunctional termination (Section VI.B.3). Note that, as in the previously discussed cases, the hydrophilic arm segments may be placed either the inner or the outer layers of the arms. 

This S5mthetic method has been extended to the direct synthesis of poly(organophosphazenes) as well as the development of star and block copolymers. For example, triarmed star-branched polyphosphazenes (eg, 6) can be synthesized through the initiation of trifimctional phosphoranimines (22). It has also been shown that the presence of living active sites at the termini of the poljuner chains allows for addition of a second monomer and the formation of block copolymers (23), such as (7) which is formed through the initiation of a difunctional linear phosphoranimine and the subsequent introduction of two different monomers (24). These developments offer the prospect of improved routes... 

Typical SAXS/WAXD spectra are shown in Figure 1 for the SEL-4,7/20/1.8 copolymers for a crystallization temperature of 313 K. The SAXS spectrum taken immediately before the T-jump indicated only a minor contribution from concentration fluctuations at 383 K. This is a result of the compatibility of PS and PCL in the melt state (8) and of the star architecture with PEO which further increases the intrinsic compatibility of the copolymer (9). After about 500 s the WAXD patterns develop peaks corresponding to the monoclinic unit cell of PEO. Notice that the crystallization of the shorter block is suppressed in the triarm star. At the same time the SAXS peaks develop signifying the formation of the PEO crystalline lamellar. 

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