Sequence Controlled Self-Knotting Colloidal Patchy Polymers

Category: Scientific Highlights

Published in Physical Review Letters

ABSTRACT:

Knotted chains are a promising class of polymers with many applications for materials science and drug delivery. Here we introduce an experimentally realizable model for the design of chains with controllable topological properties. Recently, we have developed a systematic methodology to construct self-assembling chains of simple particles, with final structures fully controlled by the sequence of particles along the chain. The individual particles forming the chain are colloids decorated with mutually interacting patches, which can be manufactured in the laboratory with current technology. Our methodology is applied to the design of sequences folding into self-knotting chains, in which the end monomers are by construction always close together in space. The knotted structure can then be externally locked simply by controlling the interaction between the end monomers, paving the way to applications in the design and synthesis of active materials and novel carriers for drugs delivery.

 

Figure: Folding free energy landscape F(DRMSD)/kBTRef of the designed patchy polymer (a) Min20T=0.4 and (b) Min50T=0.4 as a function of the distance root mean square displacement DRMSD from the target structure. The target structures are shown in the right insets and the structures corresponding to the free energy minima are shown in the top left insets. We have painted each segment type with a different color to highlight the sequence along the chains (for M=2 neutral particles are colored in gray while the attractive ones are colored in green). In (a) we plot the free energy for the short N=20 chain scenario at T=0.4 below the folding temperature TF (red continuous curve), at T=0.9 close to TF (blue dot-dashed line), and at T=1.0 above TF (black dashed line). The plot in (b) shows the folding of the long chain with N=50 at T=0.6 below the folding temperature TF (red continuous curve), at T=0.9 close to TF (blue dot-dashed line), and at T=2.0 above TF (black dashed line).

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