Smart responsive materials can undergo reversible physical or chemical changes in response to external stimuli (such as temperature, pH, light, humidity, etc.). Through molecular design and functional modification, silicone rubber can achieve various smart responsive properties, holding broad application prospects in biomedicine, sensors, soft robotics, and other fields.
Thermosensitive silicone rubber is realized by introducing polymer segments with a lower critical solution temperature (LCST). For example, grafting poly(N-isopropylacrylamide) (PNIPAM) onto the surface of silicone rubber causes the PNIPAM segments to transition from hydrophilic to hydrophobic when the temperature exceeds the LCST (approximately 32°C), leading to significant changes in the surface wettability of the silicone rubber. This thermosensitive silicone rubber can be used in controlled drug release systems, where drugs are released at body temperature (37°C) and stop at low temperatures (25°C). Additionally, by regulating the molecular weight and grafting density of PNIPAM, the response temperature range can be precisely adjusted (25-40°C).
pH-responsive silicone rubber is achieved by introducing acidic or alkaline groups. For example, introducing carboxylic acid groups (-COOH) into the side chains of silicone rubber results in protonation of the groups at pH < 4, making the surface hydrophobic, and deprotonation to -COO⁻ at pH > 6, making the surface hydrophilic. This pH-responsive silicone rubber can be used in smart valve systems to control drug release rates based on changes in body fluid pH. Experiments show that in pH 1.2 (simulating gastric juice), the drug release rate is 10%/h, while in pH 7.4 (simulating blood), it increases to 50%/h.
Photo-responsive silicone rubber is realized by doping with photochromic molecules or photothermal conversion materials. For example, embedding azobenzene molecules into a silicone rubber matrix causes the azobenzene to transition from trans to cis under ultraviolet light (365 nm), leading to reversible shape changes (bending or contraction) in the silicone rubber. This light-driven silicone rubber can be used as actuators in microrobots to perform actions such as gripping and moving under light control. Additionally, combining the photothermal effect of carbon nanotubes, photothermal-responsive silicone rubber can be prepared, which rapidly heats up (5°C/s) under near-infrared light (808 nm), enabling applications in tumor hyperthermia or shape memory recovery.
Fluoro Silicone Gum
