The phase separation and morphology in poly(urethane urea)s were investigated as soft segment length and chain extender structure were varied. Increases in soft segment length led to increased phase separation that resulted in greater mobility of the soft segment. This was shown by lower soft segment glass transition temperatures in differential scanning calorimetry (DSC) as well as a shift of Emax″ and tan δmax to lower temperatures. Also the structure of the chain extender affected the degree of phase separation and mixing of the soft and the hard blocks in an interphase. Atomic force microscopy (AFM) was used to visualize the structure of the phase‐separated domains. The hard domains were in the form of spheres 5–10 nm, or long needles 5 nm thick and 50–300 nm long. As the soft segment length increased, there were more pure soft segment phase areas between the hard domains. At high hard segment content, a larger scale structure was found, consisting of both hard and soft segments.DSC thermograms of poly(urethane urea)s containing different soft segment lengths.magnified imageDSC thermograms of poly(urethane urea)s containing different soft segment lengths.
Summary: Polyvinylpyrrolidone (PVP) is a synthetic, non‐toxic, water‐soluble polymer commonly used in a wide range of applications including several pharmaceutical applications. One example of an important application is the controlled release and delivery of therapeutic agents into sites of inflammation or tumours. However, PVP lacks reactive groups, which limits the possibility of adding new functions to the polymer in order to modify its physical and chemical properties. Furthermore, large differences in radical reactivity between 1‐vinylpyrrolidin‐2‐one (NVP) and most other monomers lead to compositional drift during copolymerization. This complicates the introduction of reactive groups into the polymer using this method. Monomers that are derivatives of NVP itself are expected to show smaller differences in radical reactivity and therefore provide a way of preparing PVP with adjustable properties. Here we present the synthesis of five NVP‐based monomers and their use in the preparation of functional PVP with adjustable properties in terms of solubility, loading of functional groups, and molar mass. The results show the possibility of tailoring PVP for different biomedical applications e.g. drug delivery systems.Copolymers from 1‐vinylpyrrolidin‐2‐one.magnified imageCopolymers from 1‐vinylpyrrolidin‐2‐one.
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