Solvent polarity, effect, grafted

Apart from the chemical effects of solvent as hydrogen donor, being heterogeneous systems, an important role of solvent is to provide appropriate reaction sites on the balance of solvent interactions with base polymer and growing graft chain. For the study of solvent effects, AM is not an adequate monomer since it is scarcely soluble in non-polar solvents. Instead, acrylic acid(AA) was employed and photografting was conducted as shown in Figure 8. 

The inclusion of mineral acid in the grafting solution has recently been shown to increase the radiation copolymerisation yield, particularly when styrene is grafted to trunk polymers like wool (3) and cellulose (4) i.e. polymers which readily swell in polar solvents such as methanol. This acid effect is important since for many copolymerisation reactions, relatively low radiation doses are required to yield finite graft. The process is particularly valuable for monomers and/or polymers that are either radiation sensitive or require high doses of radiation to achieve the required graft. 

The HPC could only with difficulty be washed off the particle surfece only those solvents which had solubility parameters close to that of polystyraie (such as ethoxyethanol) were effective in removing the stabilizer without at the same time dissolving the polystyrene particles completely. In this way, about 78% of the labelled stabilizer could be recovered. Gtx)d solvents for the HPC moiety (water and polar alo ols) removed less than 5% of the grafted stabilizo. Further proof that the stabilizer was irreversibly grafted came from the ct that when the stabilized particles woe dissolved in dioxane (a good solvent for all the components), the addition of methanol (a non-solvent for polystyrene) produced stable polystyrote particles once more. In comparison, when simple mixtures of polystyrene and HPC were treated in this way, coalescence occurred. 

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