Synthesis,Properties And Applications Of Amphiphilic Copolymers

Amphiphilic copolymers consisting of hydrophilic and hydrophobic segments were widely applied in biomedicine,catalysis,separation,photovoltaic,microelectronics and coatings.The hydrophobic chains provided their good compatibility with non-polar polymers and played an important role in the modification of general plastics.The traditional water-soluble modifiers used for hydrophilic modification of general plastics mostly have problems such as poor compatibility with matrixs and easy migration,which can avoid by using amphiphilic polymers.The objective of this paper was to develop a simple synthesis strategy with features of low-cost and easy turning the composition of amphiphilic copolymers and explore their applications as modifiers in general purpose plastics.In this paper,a series of amphiphilic copolymers were synthesized by the copolymerization of hydrophilic monomers and hydrophobic monomers.The kinetics and reaction conditions of the copolymerizations were studied.The effects of copolymer composition and topological structure on the properties of amphiphilic copolymers were also studied.Then,they were applied in PVC catalytic antifouling ultrafiltration membrane,low-density polyethylene（LDPE）hydrophilic modification,PVC hydrophilic coating,and as a dispersant for dispersion polymerization.The main results of the study are as follows:1.The copolymerization of vinyl chloride monomer（VCM）and maleamic acid（MALA）was conducted by self-stabilized precipitation polymerization.The as-prepared PVMA copolymer with-COOH and-NH₂ was employed as a modifier for PVC to prepare a Pd-loaded PVC/PVMA ultrafiltration membrane.The PVMA has good compatibility with PVC and provides bonding sites for Pd（0）catalysts.When the addition of PVMA increased from 0 wt%to 50 wt%,the porosity of ultrafiltration membranes increased from 74.7%to 88.6%,and the pure water flux reached to 691.7 L·m^-2·h^-1 which was nearly 10.6 times of pure PVC(64.7 L·m^-2·h^-1).The pure water contact angle of PVMA-50 was 74^oand dropped to 24^o in 100 s.The Pd-loaded PVC/PVMA ultrafiltration membrane had great advantages in removal of dye with high water flux by coupling catalysis and separation processes.The apparent kinetic reaction constant of Pd（1.05 wt%）-PVMA/PVC-50 is as high as 2.65×10^-3 s^-1.At a low operating pressure of 0.08 MPa（G）,the pure water flux of the Pd（0.84 wt%）-PVMA/PVC-40 membrane is up to 208.75 L·m^-2·h^-1and the removal efficiency is greater than 90%for 4-nitrophenol（4-NP）solutions at concentrations of 50ppm and more than 97%at a concentration of 10 ppm over three cycles.The content of 4-NP in wastewater treated by Pd-PVMA/PVC ultrafiltration membranes can be as low as 0.19 ppm.2.The radical solution copolymerizations of VAc with vinyl neopelanoate（VV-9）,vinyl neodecanoate（VV-10）and 2-ethylhexanoic acid（VV-EH）were investigated.The reactivity ratios were r _VAc=0.94,r _VV-9=0.96;r _VAc=1.24,r _VV-10=0.90 and r _VAc=1.31,r _VV-EH=0.82 at 65°C,respectively.The copolymerization of VAc and VV-9 demonstrated an ideal azeotropic copolymerization.By simply adjusting the feed ratios,poly（VAc-co-VV-9）（PVV）with different compositions have been successfully prepared.Terpolymers of vinyl carboxylates,VAc and vinyl alcohol with different compositions have been successfully obtained by alcoholysis under alkaline conditions.3.The terpolymer of VAc,VV-9 and vinyl alcohol（PVVOH）obtained by alcoholysis of PVV was used as a dispersant of styrene polymerization and blending modification of LDPE.The size of monodispersed polystyrene particles prepared by dispersion polymerization with PVVOH-40 was 2.0～6.0μm.As a proof-of-concept,the application of PVVOH as modifiers to improve the adhesive,hydrophilic and oxygen barrier properties of LDPE was evaluated.The PVVOH-40 was blended with LDPE and the dispersed PVVOH microdomains with a size of about 1μm.There was no obvious two-phase interface in the PVVOH-40/LDPE blend,which indicated that the long alkyl branched chains of the VV-9 units enhanced the compatibility of PVVOH and LDPE.The water contact angles of the PVVOH-10/LDPE blend reduced from104±0.9°（pristine LDPE）to 59±0.9°and retained after being soaked in water at ambient for 30 days.PVVOH is also effective in improving the adhesion between LDPE and aluminum alloys.With the addition of 25 wt%PVVOH-20,the ultimate shear strength of the lap joint was effectively enhanced from3.6±0.17 MPa（pristine LDPE）to 4.9±0.02 MPa.Furthermore,the addition of20 wt%PVVOH-10 reduced the oxygen transmission rates of LDPE film from145.3 cm³·m^-2·day^-1·bar^-1 to 52.2 cm³·m^-2·day^-1·bar^-1.4.The reversible addition-fragmentation chain transfer（RAFT）polymerization of VAc and VV-9 was studied,and the effects of RAFT chain transfer agents,molar ratio of monomer（M）to RAFT chain transfer agents,and2,2’-azobis（2-methylpropionitrile）（AIBN）initiator concentration on the synthesis of the homopolymer of VAc（PVAc）,VV-9（PV9）and the copolymer of VAc and VV-9（PVV）were investigated.Compared with 2-Cyanomethyl-N-methyl-N-phenyldithio-carbamate（CMPCD）of dithiocarbamates,the RAFT chain transfer agent S-（cyanomethyl）O-ethyl carbonodithioate（CMX）of xanthate controlled the polymerization of VAc and VV-9 much better.The molecular weight distribution of PVAc and PV9 prepared by CMX is narrower（M_w/M_n=1.29,1.20）.PV9 and PVV macromolecular chain transfer agents could be prepared efficiently in ethyl acetate solvent,at[M]/[CMX]/[AIBN]=300/3/1（mole）.PV9-b-PVAc and PVV-b-PVAc block copolymers with different compositions were prepared by using the synthesized macromolecular chain transfer agents.By subsequent alcoholysis,the amphiphilic block copolymers PV9-b-PVOH and PVV-b-PVOH were obtained and applied as hydrophilic coatings of PVC,LDPE an PP films.The modificated PVC films had excellent hydrophilicity and surface smoothness.The hydrophilicity of PVC films increased with the increase of the length of the hydrophilic chains of the amphiphilic polymer,and the contact angle reached to 70.3±1.9°after soaking in water for 30 days.The contact angles of LDPE and PP coated with PV9-b-PVOH-4 were 67±1.0°and 66±0.8°.5.The homopolymers of VV-10（PV10）and VV-EH（PVEH）were prepared by RAFT polymerization with the[M]/[CMX]/[AIBN]=300/3/1（mole）,and the monomer conversion could reach over 80.0%.When the conversion was lower than 80.0%,PV10 and PVEH macromolecular chain transfer agents with narrow molecular weight distribution（M_w/M_n<1.25）could be obtained.The PV9-b-PVP,PV10-b-PVP and PVEH-b-PVP amphiphilic block copolymers were successfully synthesized by prepared macromolecular chain transfer agents.By tuning the ratio of NVP to PV9 macromolecular chain transfer agent,PV9-b-PVP amphiphilic block copolymers with different lengths of hydrophilic chain were obtained,and their hydrophilicity increased with the increase of PVP chains.PV9-b-PVP amphiphilic block copolymers could self-assemble in a mixture of isopropyl alcohol and water,and fibrillar and single dispersed microspheres micelles were obtained by changing the ratio of alcohol and water.The contact angle of LDPE film coated with PV9-b-PVP-4 with NVP content of 16.3 mol%was 62±0.9°,which was significantly lower than that of LDPE film（104±0.9°）,and remained for 10 days,soaking in water.