Precise Synthesis of Poly(macromonomer)s Containing Sugars by Repetitive ROMP and Their Attachments to Poly(ethylene glycol): Synthesis, TEM Analysis and Their Properties as Amphiphilic Block Fragments

Various poly(macromonomer)s (PMMs) have been prepared by a repeating ring opening metathesis polymerization (ROMP) technique using the well‐defined molybdenum initiators of the type, [Mo(CHCMe2Ph)(NAr)(OR)2] with OR=OCMe3, OCMeC(CF3)2; Ar=2,6‐iPr2C6H3, 2,6‐Me2C6H3. The synthetic strategy is based on the polymerization of norbornene and its derivatives affording di‐ and triblock side chains bearing sugars (mannose, galactose, glucose etc.), linked via O‐ (ester), and glycosidase resistant C‐ (isoxazoline) glycosides. The efficient placement of norbornene units on the side chain termini and their conversion into PMMs, facilitated by the Mo alkylidenes, proceeded in a living manner with the quantitative initiation. The methodology was applied to prepare poly(macromonomer)‐graft‐PEG [PEG: poly(ethylene glycol)], by the attachment of a pseudo phenol terminus on the PMM main chain to PEG‐Ms2 [MsO(CH2CH2O)nMs, Ms=MeSO2] using a “grafting to” approach. Removal of the acetal protecting groups from the sugar coating of a variety of supramolecular structures including PMMs, linear amphiphilic block copolymers (ABC) and a PMM‐graft‐PEGby using trifluroacetic acid/water (9:1), and suspension in water, prompted the spontaneous formation of spherical architectures by self‐assembly of the amphiphilic PMMs as observed by transmission electron microscopy (TEM). The ability to uptake the hydrophobic dye (Nile Red) into the micellar cores of a variety of amphiphilic polymeric fragments is a significant step towards the production of sugar‐coated nanospheres for cell‐targeting biomimetic applications. Precise control of amphiphilic blocks: Efficient preparation of poly(macromonomer)s (PMMs) containing (acetal, acetyl) protected sugars (PMM‐graft‐PEG) was achieved by the repetitive living ROMP technique. Removal of the protecting groups from the sugar afforded various supramolecular structures, prompting the formation of spherical architectures by self‐assembly (see picture).