Colloidosomes and stretchable hydrogels prepared from pH-responsive microgels and nanogels

  • Wenkai Wang

Student thesis: Phd


This thesis presents a study towards a new concept which would use inter-crosslinked microgels to prepare double crosslinked hydrogels with high internal porosity. In the initial research a convenient method to form the doubly crosslinked pH-responsive colloidosomes was demonstrated. The colloidosomes were made by functionalised microgels of particles poly(ethylacrylate-co-methacrylic acid-co-1,4-butanediol diacrylate)-glycidyl methacrylate (GMA-MG). First of all, the non-functionalised microgels particles poly(ethylacrylate-co-methacrylic acid-co-1,4-butanediol diacrylate) (MGs) and GMA-MGs were prepared used emulsion polymerisation. The latter were then used to stabilise emulsions particles preparing the colloidosomes. The oil/water interface promoted sufficient microgel deformation and interpenetration to enable covalent inter-linking of peripheral vinyl groups on the microgel particles via free-radical coupling using UV light. Uniquely, our method for DX MG-colloidosome preparation used only one type of (colloidal) building block for shell assembly. It also showed that the doubly crosslinked pH-responsive colloidosomes had similar pH-responsive swelling properties as the GMA- MGs. The initially established method for pH-responsive colloidosomes preparation was not compatible with scale up, which limits its potential for use. Therefore, in the next research, we established the best conditions to prepare the stable Pickering emulsion which used an ethylacrylate based microgels (EA-MGs) system. Furthermore, we demonstrated a general, gram scale method, which used high shear rate and thermal reaction to form the smallest pH-responsive microgel colloidosomes yet reported. It also showed that the doubly crosslinked pH-responsive colloidosomes had a selective pore size, which could be varied with pH. The properties of these microgel colloidosomes dispersions imply that they have good potential for future application as injectable gels for release and delivery applications. After the research of colloidosomes, because of the limitation of the mechanical and release property of the colloidosomes, we required more stretchable particles while the gels used above in the colloidosmes were brittle. Accordingly, new particles were synthesised by emulsion polymerisation of methyl methacrylate, methacrylic acid and without any crosslinking monomer. This is a new nanogel-based approach for preparing highly stretchable -COOH-rich hydrogels. The NGs had very high MAA content (84 mol. %). And the latter were vinyl functionalised and gave dispersions that could be crosslinked to form highly stretchable gels. The gels could form any shape and could be tied in knots and stretched considerably without damage. The DX NG gel prepared at pH 10 could be stretched to more than 250% of its original length. The maximum compressive strain for the covalent interlinking of these NGs prepared at pH 10 was 93 % without breaking. This is the highest value reported for a DX NG system to date. It also gave highly-stretchable pH-responsive DX NGs with a stretchability of up to 520%. The results of this study provide design tools for improving DX NG ductility and hence increasing the range of potential applications for this new class of hydrogel and DX pH-responsive NG-colloidosomes in future.
Date of Award1 Aug 2018
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorBrian Saunders (Supervisor) & Christopher Blanford (Supervisor)


  • Colloidosomes
  • hydrogels
  • nanogels
  • pH-responsive
  • microgels

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