Investigating the influence of nucleobase interactions on block copolymers self-assembly in aqueous solution

Thomas, Marjolaine (2022). Investigating the influence of nucleobase interactions on block copolymers self-assembly in aqueous solution. University of Birmingham. Ph.D.

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Abstract

Nucleobase-containing synthetic polymers have been extensively studied for their ability to mimic DNA and for their specific and complementary hydrogen-bonding interactions. The primary aim of this thesis was to explore the pathway dependence of morphologies from polymer self-assemblies through interactions between complementary nucleobase- containing polymers synthesize via reversible addition-fragmentation chain-transfer (RAFT) polymerization. In Chapter 1, nucleobase-containing acrylamide monomers were synthesized, and their corresponding synthetic diblock copolymers were prepared via RAFT polymerization. Well defined thymine-containing spherical micelles were formed in aqueous solution via self-assembly of the amphiphilic copolymers, with the nucleobase-containing segments in the core of the nanoparticles. Following the self- assembly, copolymers with the complementary nucleobase were introduced into the micellar solutions. The influence of the core and/or the corona block length on this morphological transformation mechanism was studied, and these results highlighted that by making straightforward adjustments to the polymers involved in the process, nanoparticle dimensions could be tuned in a control manner.
A novel methodology for the fabrication of nucleobase-containing nano-objects of controllable size and shapes was then developed in Chapter 3, polymerization-induced self-assembly (PISA) in aqueous solutions. It was employed for in situ preparation of nucleobase-containing block copolymers nano-objects via aqueous reversible addition- fragmentation chain-transfer (RAFT) polymerization allowing to access long adenine- containing polymer chains at relatively high concentrations and highlighted the potential of this method for understanding fundamental self-assembly process during PISA route. Various nano-objects of different morphologies were obtained by this method (i.e., spheres, worms, and vesicles), and access to higher DPs compared to conventional RAFT polymerization was achieved. This work highlights the potential of aqueous RAFT- mediated PISA as a method to access longer polymer chains for adenine-functionalized monomer and these nano-objects as platforms for understanding fundamental self- assembly process during the PISA process.
In particular in Chapter 4,vesicles adenine nano-objects (PAn) showed a controlled shape transformation induced by the addition of a complementary base-paired polymer. The addition of a complementary short thymine polymer (PT20n) into a PAn solution induced deformations into the vesicular membrane of PAn and increasing the amount of PT20n led to node growth and eventual detachment. .Quantitative analysis of nano-object shapes revealed that the extent of deformation of PAn correlated to the amount of added PT20n. Confocal experiments confirmed that the shape transformation was due to the complementary interaction of the nucleobase moieties contained in the block copolymers. This result suggests that vesicle shape transformations can be controlled by externally added a complementary nucleobase-containing to the membrane, which can serve as a potential method for further understanding of membrane curvature process. Furthermore, polymer insertion induced shape changing could open up new routes for the design of new functional complex shapes nanocarriers and nanomachines for diverse applications.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):