CONCLUSIONS thesis synthesis and characterization of

1 0 1

Chapter V CONCLUSIONS

Melt polymerizations to form polyesterpolydimethylsiloxane segmented copolymers with high molecular weights were successful using either 1° or 2 ° amino alkyl functional oligomer. In these investigations an upper limit of about 40 weight percent siloxane was observed, otherwise macrophase separation resulted and reasonable molecular weights could not be achieved. In this research, a polydimethylsiloxane oligomer was chosen to minimize this phenomenon. Oligomers with smaller molecular weights may allow higher weight percent siloxane contiaining copolymers. Compression molding above T m of the well defined copolymers resulted in tough, ductile films. The ability to compression mold these materials was of importance, since may polysiloxane copolymers are difficult to process in the melt due to their macrophase separation, even when above T m . Multiple transitions corresponding to the polysiloxane and polyester phases were observed in both dynamic mechanical and differential scanning calorimetry experiments. This evidence supports the possibility of microphase seperation. However, some phase mixing may be occuring as evidenced by melting point and glass transition temperature behavior. Under the reaction conditions described, the titantium isopropoxide catalyst does not cause degradation or redistribution of the polysiloxane oligomer during copolymerization. The soluble cycloaliphatic segmented copolymers allowed for removal of any unincorporated polysiloxane via precipitation techniques. Studies revealed little if any polydimethylsiloxane was unincorporated using the reactions described. The segmented polyesterpolysiloxane copolymers exhibited better mechanical properties than the polyester homopolymers. Copolymer molecular weight was heavily dependent on the ability to achieve high vacuum in the final step of the reaction sequence to allow removal 1 0 2 of the excess diol. This forced the reaction to completion and with carefully controlled stirring rates and high temperatures, high molecular weights could be achieved. 1 0 3

Chapter VI SUGGESTED FUTURE STUDIES