Synthesis and surface characterization of copolymers containing low-molecular weight amino-propyl-terminated siloxanes

Poly(dimethylsiloxane)s(PDMS) are often incorporated into copolymers and polymer blends due to their unique properties including, low surface energy, high gas permeability, excellent oxidative stability, low dielectric constant, low glass transition temperature (T_g), low moisture absorption and high flexibility. Due to the low surface energy of the PDMS with respect to most other materials, there is usually preferential segregation of the siloxane component to the surface in copolymer systems and blends, resulting in a surface that is comprised primarily of PDMS. This means that while the surface properties are dominated by the PDMS component of the copolymer, the overall bulk properties will be representative of both components (depending on the composition).; The extent of this preferential siloxane segregation is dependent upon many factors including casting solvent, block length, and bulk composition. In this dissertation, the effects of varying the siloxane segment length composition on the surface properties of two different copolymer systems is described. Chapter 2 focusses on the synthesis and bulk characterization of two very important siloxane containing copolymers, poly(imidesiloxane) and poly(ureaurethane)-PDMS copolymers, which were developed as adhesive materials and anti-fouling coatings respectively.; Chapters 3–5 focus on the surface characterization of these two copolymer systems utilizing both X-ray Photoelectron Spectroscopy (XPS) and Time of Flight-Secondary Ion Mass Spectrometry (TOF-SIMS). Angle Dependent XPS has been successfully used to obtain deconvoluted depth profile information from these copolymer surfaces. This process however is very controversial, and not enough is known about the accuracy of such a method. This process is therefore described in detail in chapter 3, where the accuracy of the surface overlayer thickness of PDMS is determined through comparison to a model system used to describe chain dimensions. The accuracy is further investigated utilizing a reference material containing poly(methylmethacrylate) (PMMA) on Si.; Chapters 4 and 5 are detailed surface investigations of poly(imidesiloxane) and poly(ureaurethane)-PDMS systems respectively, where both XPS and TOF-SIMS are utilized to determine the surface characteristics of copolymers containing varying siloxane segment length compositions and how they relate to their respective applications. Chapter 5 describes the first comprehensive TOF-SIMS study on the preferential segregation of PDMS segment lengths in complex copolymer systems. All of the results were consistent with a model of the surface, which has longer siloxane chain lengths preferentially segregating to the surface and dominating the surface properties.