Semicrystalline block copolymers, variation

Effects of Variation of Composition and Block Sequence on Properties of Copolymers Containing Semicrystalline Block(s)... 

In this study, the effects of the variations in block sequence and composition (and thus relative block length) on the material properties of two series of triblock copolymers has been investigated. One of the blocks, the hydrogenated polybutadiene (HB), is semicrystalline, and the other block, the hydrogenated polyisoprene (HI) is rubbery at room temperature. Thus in one series, the HBIB block copolymers, the end blocks are semi-... 

Figure 13.5 shows the variation of melting and crystallization temperatures corresponding to each semicrystalline block within PLLA-6-PCL diblock copolymers as a function of composition [34]. For comparison purposes, solution blends of PCL and PLLA homopoljuners of equivalent molecular weights to those of the diblock copolymers were prepared and their characteristic transition temperatures were also reported in Fig. 13.5. This figure shows that the prepared PLLA and PCL blends are immiscible for the compositions examined as can be gathered by the invariance of the melting points associated with each homopolymer. Instead, the diblock copolymers exhibit signs of miscibility. In particular, the melting temperature of the PLLA block decreases as the content of PCL increases, and in the case of the L32C68 sample, the melting point depression of the PLLA block reaches 11°C.

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