Preparation And Controlled Release Of Nanoparticle Encapsulated DCOIT And MD Simulation Research

In the past decades,the poisonous residues released from the antifouling?AF?paints have become an urgent and serious problem in offshore marine,which drove the development of the improved AF technologies.Among these promising AF technologies,the controlled release of the antifoulant,which could be response to the characteristic of the marine biological reproduction,became a realistic and useful method,however,this method has been not paid more attention yet.Therefore,in this paper the nanocapsule containing the antifoulant was prepared with miniemulsion polymerization and showed the feature of thermal-responsive within its shell because the ratio of three state structured water changed as marine temperature varied,and the release of the antifoulant in nanocapsule could be adjusted.The factors of miniemulsion were investigated,the composition of the shell was characterized by FT-IR and ¹H-NMR,the appearance of nanocapsule was analyzed by TEM,and the hydration structure within polymer as well as the relation of monomers and the encapsulation efficiency were analyzed.At same time,according to the marine environment,the research was been going about the equilibrium swelling of the shell polymer,the physical properties of the swollen shell,the dynamics of the swelling systems,the diffusion of the antifoulant in the swollen polymers were investigated,and all of these work could explain the controlled release of the antifoulant by ambient temperature.Therefore,our works followed as blow:A,The nanoparticles were synthesized via miniemulsion polymerization of methyl methacrylate?MMA?,n-butyl methacrylate?n-BMA?,methacrylic acid?MAA?,N-n-propylacrylamide?NNPAAm?.The structure and composition of the shell copolymer were characterized with FT-IR and ¹H-NMR,and the composition of shell was P?MMA-co-n-BMA-co-MAA-co-NNPAAm?.The dimension range of the nanocapsule was decided by evaluating the effect of the surfactant on the diameter of the nanocapsule,and it was confirmed that NNPAAm component was not enrichment in nanocapsule surface,but distributed random in polymeric chain by measuring diameter of nanocapsule in different temperature and by analyzing the element distribution on the surface of the nanocapsule with XPS.The effect of the oil components of miniemulsion on the structure of nanoparticles were investigated by TEM,and the nanocapsule was prepared successfully with containing NNPAAm in the shell.B,Based on that water content was the important factor for the controlled release,the hydration structure and three state structured water in the shell polymer were investigated to explain the thermo-sensitive mechanism.At first,three kinds of swollen P?MMA-co-n-BMA?s were simulated by MD,and the water content was up to 26.96%at equilibrium swelling.The salvation free energy of water in swelling process,RDF between oxygen atom and water and the distribution of the three state structured water in the shell were studied,it concluded that the van der Waals interaction and the carbonyl oxygen played the critical roles in the swelling process.The swelling process followed as below:water molecules permeated into P?MMA-co-n-BMA?,it formed non-freezing water preferentially and bound with carbonyl oxygen atoms through hydrogen bonding;as the water content increased,freezing water and free water occupied more of the interior space away from the carbonyl oxygen atoms.The amount of non-freezing water remained constant once the swelling reaches equilibrium,which implied the saturation of the hydrogen bonding interaction between the carbonyl oxygen atoms and water.At same time,hydration layer of PNNPAAm was characterized by FT-IR,and the characteristic absorption peak of OH group was found at 3365.93 cm^-1 when the ambient temperature is below 295.5 K?22.5??and was found at 3377.67 cm^-1 when the ambient temperature is over 295.5 K because freezing water transferred into free water.The shell was investigated by DSC and showed there was freezing water and free water when the shell copolymer or nanocapsule was moist.C,The decreases range of Tg were 21.72 K to 14.40 K when P?MMA-co-n-BMA?s were at equilibrium swelling and water had the dynamical property as the same level as those of the bulk water.Three state structured water were analyzed individually and it concluded that non-freezing water and free water also had the same dynamics with the bulk water.The free volume of the dry-swollen matrix is higher 3.62 times than that of the dry polymer with the rolling size of 1.0?,and the free volume in the dry-swollen matrix only decreased from approximately 12,000?³to approximately 7,800?³ when the radius of the rolling probe increased from 1.0?to 3.8?,it depicted that the swollen matrix could indeed accommodate 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one?DCOIT?combined with the higher mobility than the polymer chain by over two orders of magnitude.At last,the MSD of analysis further showed that non-effective motion of DCOIT attributed to the jump or trapped motion at low temperature?the glassy state?,but at 308 K?the rubbery state?continuous-motion occurred,resulting in significant displacement in the swollen matrix.D,The antifoulant was encapsulated in miniemulsion polymerization successfully.The element distributions on the surface of four samples were characterized by XPS,and it confirmed that the antifoulant has been encapsulated at the core of nanocapsule.Encapsulation efficiency of DCOIT was measured by High performance Liquid Chromatography and the effect of the factors including MAA,HD,crosslinking agent and DCOIT on the encapsulation efficiency were evaluated,an ideal condition was concluded with the encapsulation efficiency as high as89.16%.At last,the diffusion of encapsulated DCOIT was evaluated in different temperature,it was found a sharp increase between the release rate between 294 K to307 K,where the release rate of DCOIT was times higher than that of the temperature range from 278 K to 288 K,and the releasing rate kept constant when ambient temperature was as high as 313 K.It depicted that the release of DCOIT from the nanocapusle could be controlled by the ambient temperature and the release rate had a maximum value when the swelling reached equilibrium.