Precision Macromolecular Chemistry
The ultimate goal for every synthetic polymer chemist is the extensive control on the final properties of a desired product. Thus, control on the molecular level is inevitable.
Our group is specialized on the synthesis of precisely tailored polymers. Therefore, taking advantage of modern polymerization techniques (e.g. ATRP, NMP, RAFT polymerization, ROMP, ROP, ADMET), subsequently, we are combining this approach with post-polymerization modification techniques on the basis of click chemistry. As a consequence, we achieve full control of polymer architecture and the polymers functionality.
Our approaches...
There are several possibilities to alter polymeric functionalities. Changing the monomer is one option, modifying the monomer prior to polymerization is another one. However, utilizing polymer analogues reactions has the advantage of using solely one monomer for polymerization and subsequently modifying the defined polymer chain with multiple functionalities. Thereby, the polymerization degree maintains unchanged.
In order to achieve full control of the polymer architecture and functionality, we concentrate on the development of new monomers that enable an efficient and robust post-polymerization functionality. An inherent reactive character is necessary in order to guarantee a quantitative modification under mild conditions, i.e. room temperature. In the past, we have thus been able to promote the use of activated esters within polymer science, namely the use of pentafluorophenyl (PFP) esters. PFP esters have been prepared from acrylates, methacrylates, 4-vinylbenzoates, norbornene-carboxylic acids, etc.
Besides, we investigated the use of methyl salicylate acrylate ester as an alternative to PFP, being less cytotoxic compared to common active esters. This approach is interesting regarding approaches in the field of biological active polymers for in vivo application. Aside of active ester chemistry, we are using the whole toolbox of post-polymerization techniques in order to gain full control on the final polymer characteristics.
Our most recent achievements and goals...
We are constantly searching for new possibilities to push the limits of post-polymerization modification. For instance, the exact positioning of a single PFP-ester functionality in a polymer chain enabled the formation of well defined polymer structures, e.g. we investigated the formation of four-arm star-shaped polymers.
Exact positioning of a single PFP functionalty in a linear polymer chain is followed by simple amidation and results in a three-arm star-shaped polymer. Furthermore, a subsequent Mitsunobu-reaction allows the attachment of a fourth arm.
In another study we are currently investigating the influence of high density functional side groups on post-polymerization modification.
Polymerization of carbene precursors leads to functional polymethylene moieties with a high density of side groups. Thus, we obtain polymeric structures bearing a functionality at every main chain C-atom. By synthesizing functional polymethylenes, we aim for exploration of the effect of high density functional side groups on post-polymerization modification and investigate the properties of the resulting polymers.
In a new study different ester reactivities can be utilized for selective base degradation. For this, poly[(pentafluorophenyl acrylate)-co-(BMDO)] was synthesized by using 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) and pentafluorophenyl acrylate (PFPA) as monomers. The addition of different amines leads to a selective amidation of the activated pentafluoro-phenylacrylate without cleaving the BMDO-ester group in the main chain. The usage of potassium hydroxide leads to a subsequent degradation of the obtained polymers.
