Multifunctional star-graft quaterpolymers PSn[P2VP-b-(PAA-g-PNIPAM)]n with two different kinds of arms: shorter PS arm and longer P2VP-b-PAA block copolymer with grafted PNIPAM chain arms, were studied at the air-water and air-solid interface. Due to the pH dependent ionization of P2VP and PAA blocks, as well as thermo-responsiveness of PNIPAM chains, the stars have complex molecular structures and multiple responsive properties to pH, temperature and ionic strength. We investigated the assembly of the star-graft quaterpolymers in Langmuir and Langmuir-Blodgett monolayers under different pH, temperature and ionic strength of the subphase, the effect of arm number (9 versus 22) and PNIPMA graft ratio on the assembled structures are also studied. The molecular area of the stars is largest at the isoelectric region, and smallest at acidic condition, which is due to the combined results of ionization of the blocks and hydrogen bonding between PAA and PNIPAM blocks. The molecular area of the stars gradually increases with temperature, which is counterintuitive, the main reason is that at low temperature PNIPAM chains are hydrophilic and tend to submerge in the subphase, and emerge to the interface with increasing temperature. Moreover, at higher surface pressure the stars tend to form intermolecular aggregates with increasing temperature. Utilization of the star polymer monolayer as smart drug carrier was also demonstrated, both hydrophobic and hydrophilic target molecules can be encapsulated within the stars simultaneously, and the controlled release can be triggered by changes in pH condition and temperature. This work is the first systematic study on the assembly of complex multi-responsive star-graft polymers at interface, which could find applications in drug delivery, microreactor, smart coatings, and biosensing.

Interfacial behavior and assembly of multiresponsive star graft copolymers

249th National Meeting (2015)

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