Preparation And Performance Of PH-Responsive Silicone-based Polyurea For Marine Antifouling Coatings

Marine antifouling materials are currently one of the main methods to prevent marine biofouling.Since organotin-based marine antifouling materials were completely forbidden in 2008,more environmentally-friendly and efficient fouling release coatings（FRCs）have been extensively reported.Silicone-based antifouling materials as a main representative of fouling release coating,due to their low elastic modulus and surface energy,can effectively remove marine fouling organisms under high-speed water flow.However,silicone-based antifouling materials have poor antifouling performance under static conditions and poor adhesion to substrates,leading to fall off in large areas.Aiming at these problems,this paper has designed a pH-responsive silicone-based polyurea marine antifouling coatings.By introducing polyurea segments and phenylborate esters,the as-prepared coatings realize high adhesion and excellent antifouling performance under both dynamic and static conditions.The research contents are as follows:（1）Chain extension reaction between aminopropyl-terminated polydimethylsiloxane and isophorone diisocyanate,then terminated by silane coupling agent,yielding the IPTS-terminated silicone-based polyurea materials（IPTS-PDMS-PU）.The pH-responsive phenylboronate groups was introduced to IPTS-PDMS-PU to prepare the composite coating PDMS-PU_ax.When the added amount of S-EU is 7%(labeled as PDMS-PU_a2),the as-prepared PDMS-PU_a2 coating realizes lower surface energy of 24.9 m J·m^-2,a good sterilization rate of 88.8%,and the highest adhesion performance rating of 0.Compared with weak alkaline environment（pH=8.2）,PDMS-PU_axcoating exhibits high S-EU release amount（increased by 47.0%in 7 days）when stored in weak acid environment（pH=5.8）as well as good pH-response performance.（2）Based on the IPTS-PDMS-PU prepared in（1）,imine bonds were further introduced by mixing 3-aminopropyltriethoxysilane and 2-formylphenylboronic acid,finally realizing the preparation of composite coatings PDMS-PU_fx.The introduction of the imine bond can serve as an acid-responsive group to increase the release rate of S-EU,and form an internal boron-nitrogen（N→B）coordination structure with phenylboronate to reduce the p Ka of phenylboronate,thus enhancing the initial loading capacity and release stability of S-EU under neutral pH condition.The as-prepared PDMS-PU_f2 coating realizes lower surface energy of 24.8 m J·m^-2,a good sterilization rate of 97.5%,and the highest adhesion performance rating of 0.Compared with weak base environment（pH=8.2）,PDMS-PU_fx coating exhibits high S-EU release amount（increased by 57.5%in 7 days）when stored in weak acid environment（pH=5.8）as well as good pH-response performance.As a result,composite coatings PDMS-PU_fx exhibit significantly enhanced initial release rate of S-EU in the simulated seawater（pH=8.2）environment,which was mainly due to the higher loading of S-EU.In addition,the initial release rate of the PDMS-PU_fx coating in neutral environment（pH=7.0）is close to that in weak alkaline environment（pH=8.2）realized higher stability in the neutral environment.