Poly(N‐isopropylacrylamide)‐Modified Styrene‐Butadiene Rubber as Thermoresponsive Material

Abstract

Narrowly distributed (N‐isopropylacrylamide) (NIPAM) polymers are prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization. After successful cleavage of the trithiocarbonate end groups (thiol generation), they can be grafted to styrene‐butadiene rubber (SBR) by a radical thiol‐ene reaction leading to various grafted SBR‐copolymers. During the grafting reaction, no crosslinking or branching of the SBR can be observed. Measurements of the contact angle of water show that the lower critical solution temperature (LCST) properties of the PNIPAM fraction affect the SBR. Films of the graft‐copolymer exhibit a distinct hydrophilicity below the LCST, while they show hydrophobic behavior above the LCST. Rheological measurements reveal a physical crosslinking of the functionalized SBR due to nanophase separation of the PNIPAM chains (hard phase) in the unpolar SBR. Compared with blends of SBR and PNIPAM, the PNIPAM‐grafted SBR possesses a much finer distribution of the PNIPAM domains (10–30 nm) within the matrix. In addition, two novel difunctional chain‐transfer agents are used, leading to difunctional PNIPAM, enabling a covalent crosslinking of SBR.

Concentration Effect over Thermoresponse Derived from Organometallic Compounds of Functionalized Poly(N-isopropylacrylamide-co-dopamine Methacrylamide)

“…This fact could be associated with the presence of the organometallic complex, which could reduce the impact of the hydrophobic contributions of DMA below LCST as was observed for the hydrophobic transitions observed by calorimetry and UV-vis spectroscopy. The results fit well with the literature as remarkable changes are exclusively observed below LCST, while above the LCST, the angle remains constant [45].…”

“…This fact could be associated with the presence of the organometallic complex, which could reduce the impact of the hydrophobic contributions of DMA below LCST as was observed for the hydrophobic transitions observed by calorimetry and UV-vis spectroscopy. The results fit well with the literature as remarkable changes are exclusively observed below LCST, while above the LCST, the angle remains constant [45]. The presence of the organometallic compound could play an important role along the transition LCST showing a clear jump which could be associated with the coil to globule transition where the organometallic moieties could be exposed outside of the globule due to its hydrophobic nature inducing those high angles.…”

“…For PNIPAM an increase in the hydrophobicity was reported, while a copolymer with hydrophilic monomer decreases the contact angle [44]. On the other hand, PNIPAM-modified styrene-butadiene rubber was also studied in terms of contact angle for different contents of NIPAM, where it was demonstrated how strongly the hydrophilic behavior could be influenced below the LCST [45]. Another important fact is associated with the trend drawn by the cloud points, which increase as organometallic moieties rise.…”

Photoinduced Electron Transfer Reactions for Macromolecular Syntheses

“…It lends all the expected advantages of a photochemical process to the reaction such as mild reaction conditions and spatiotemporal control. Groups such as Hoyle, Bowman, , Lowe and others − greatly expanded the sphere of knowledge as it applies to the applicability of the photoinduced thiol–ene click reaction toward the macromolecular synthesis of complex polymeric architectures. Hawker and co-workers have demonstrated the thiol–ene click reaction’s utility for rapid complex dendrimer formation. − Du Prez and co-workers have used the thiol–ene click reaction to fashion diblock and star-shaped polymers …”

Fabrication of Single Cylindrical Au-Coated Nanopores with Non-Homogeneous Fixed Charge Distribution Exhibiting High Current Rectifications

“…S -1-Dodecyl- S -(α,α′-dimethyl-α″-acetic acid)­trithiocarbonate (DMP) was synthesized following the previously reported procedure . For the reversible, addition–fragmentation chain transfer (RAFT) polymerization, N -isopropylacrylamide (1.50 g, 13 mmol), DMP (48.3 mg, 0.13 mmol) as a chain-transfer agent (CTA), azoisobutyronitrile (2.2 mg, 0.013 mmol) as an initiator, and 2 mL of dioxane were added to a Schlenk tube following a previously described method . The oxygen was exchanged by nitrogen by applying three freeze–pump–thaw cycles.…”