原子转移自由基聚合法接枝改性纳米纤维素及其功能化应用

Chemical modification of nanocellulose via atom transfer radical polymerization:strategy,applications and challenges

纳米纤维素不仅具有天然纤维素的基本结构和特性,还具有纳米粒子的独特性能,使其成为众多领域的研究热点。然而,由于纳米纤维素表面存在丰富的羟基,导致表面化学性质单一,需要对其进行化学改性拓宽应用领域。原子转移自由基聚合法(ATRP)能够对纳米纤维素表面进行接枝改性,从而赋予纳米纤维素多样化的功能特性,是纳米纤维素高值化应用的重要方法。本文首先总结了传统ATRP法以及四种新型ATRP法在纳米纤维素表面接枝改性中的应用进展;随后介绍了ATRP法在纳米纤维素端基接枝改性中的应用进展;然后分别介绍了ATRP改性的纳米纤维素接枝共聚物在纳米复合增强、智能响应、环保和生物医疗等领域的应用研究;最后总结了ATRP法改性纳米纤维素存在的难点,并展望了未来ATRP法在纳米纤维素接枝改性领域的发展趋势。

Nanocellulose(NC)is an emerging nanomaterial which has similar structure and properties to natural cellulose.It has been an interest subject in the field of nano-reinforcement,intelligent response,environmental protection and biomedicine,due to their promising properties such as nanoscale effect,huge surface area,chiral liquid crystalline phase,high crystallinity,high transparency and high surface activity,etc.However,due to the abundant hydroxyl groups on the surface of nanocellulose,the surface chemical properties are single,which requires chemical modification to broaden the application field.Therefore,chemical modification of NC to broaden its application in the field of functional/composite materials is of great significance.Atom transfer radical polymerization(ATRP),a“living”/controllable free radical polymerization technology,is one of the most powerful and versatile process used for the synthesis of high value-added NC grafted copolymers.By ATRP grafting,various functional groups or side chains could be accurately introduced onto the surface of NC imparting with some new physicochemical properties(such as hydrophobicity,antibacterial and intelligent responsive properties,etc.).This review describes the recent advances in NC functionalization by ATRP in the past ten years and includes four parts:(1)Traditional ATRP grafting modification of NC including NC initiator,scarification initiator;(2)Surface charge of NC,size of NC as well as grafted monomer;surface grafting modification of NC via four new ATRP[including SET LRP,ARGET ATRP,ICAR ATRP and(metal free)photocatalysis ATRP];(3)ATRP of NC via end group grafting modification;(4)The application of nanocellulose grafting copolymers in nano-reinforced composites,smart response materials,environmental protection materials and biomedical materials.Finally,current challenges and future perspectives of ATRP for grafting modification of nanocellulose were discussed.