Study On The Side Chain Crystalline Polyacrylates With Temperature Sensitive

Polymer morphology is an important branch of polymer physics,including the basic morphological and structural changes during polymer crystallization and melting.The theory of polymer crystallization has got great breakthrough after several many years research,however,some basic problems are still worthy of studying.In this thesis,based on some basic problems of polyacrylates(PAAn,n: side chain carbon number) and poly(octadecyl-co-n-alkyl acrylate)s (P(AA18-co-AAn))(n is the side chain carbon number),with side chain crystallization,our studies are carried out using atomic force microscopy(AFM), Polarizing Optical Microscope(POM) and differential scanning calorimetry(DSC) to investigate the morphological and structural changes during aggregation, crystallization and melting.At the same time,for poor mechanism strength,the polyacrylates were coated on the film in packing filed.So,based on the temperature-smart application of polyacrylate in packaging,the support film of the micro core polypropylrene was studied by strengthing method.The results manifisted that the side chain carbon numbers of the acrylate homopolymers could not less than 10 if the polymer possesses the crystalline ability.And the melting point and heat fusion increased linely with the side chain carbon number.For P(AA18-co-AAn),the thermal behavior of P(AA18-co-AAn) such as melting points and heats of fusion increase with the AA18 increasing.The crystalline and melting behaviour of the copolymers of AA18 with crystalline homologswere much different from the copolymers of AA18 with non-crystalline homologous series.It is also found that the calculated values of melting points and heats of fusion fit the experimental data well to a certain degree.The results show that the anticipated material with certain temperature sensitivity can be designed through copolymerizing various acrylates.The more studies manifested that the side chain length of copolymerizing acrylate has great influence on the crystallinity(X_c),the value of extent of equilibrium crystallinity(X_c/X_cmax) and melting range of the AA18 copolymers.In copolymers of AA18 with crystalline acrylates,the X_c increases with the increasing of AA18 content,while the corresponding curves of melting range increase at first and then decrease;the X_c/X_cmax of the AA18 copolymer with AA14 or AA16 changes little,but the X_c/X_cmax of the AA18 copolymer with AA10 or AA12 increases at first and then decreases with the increasing of AA18 content.However,in the copolymers of AA18 with non-crystalline acrylates,both X_c and X_c/X_cmax increase with the increasing of AA18 content;the value of X_c/X_cmax decreases with the increasing of side chain length and the maximum of melting range is almost equal.A side-chain crystallizable poly(octadecyl acrylate)(PAA18) was prepared via atomic transition radical polymerization(ATRP).The crystal peak temperature(T_C) and melting peak temperature(Tm)are estimated from DSC measurements.The thermal behavior of P PAA18 is different from that of main chain crystallizable polymers,because PAA18 has a much smaller melting range. The crystallization morphology was investigated by atomic force microscopy (AFM) and polarizing optical microscopy.The side-chain crystallizable PAA18 shows a network morphology consisting of edge-on and flat-on lamella.In situ observation on the isothermal crystallization behavior of PAA18 was carried out with hote-stage AFM.The AFM results indicate that the edge-on lamellae formed first,and formed network morphology.The flat-on lamella appeared adjacently to edge-on lamella first than independent flat-on lamella.With the increasing of crystallization time,the two kinds of flat-on lamella filled in the network formed by edge-on lamella.When isothermal crystallized at a high temperature,PAA18 shows a growth velocity of crystals after a long induction period of nucleation, because of the appearing of large amount of flat-on lamella.The reflection absorption infra-red spectroscopy revealed that the major orientation of methyl groups in PAA18 tend to be normal to the surface.Combining the results of electron diffraction pattern,the orientation of the side chains are proposed to be normal to the surface of the polymer film,which is main reason for the forming of flat-on lamella.For the application of polyacrylates with temperature,the polypropylene micro pore sustain film was studied.The morphology and structure of a andβ-PP and the growth ofβcrystal induced by nucleating agent are studied by several methods such as Atomic Force Microscopy,Differential Scanning Calorimetry, Scanning Electronic Microscopy(SEM) and Polarized Optical Microscopy.The effect of technical factors on the morphology and structure of the PP precursor sheets are discussed.The results show that there are significant differences in morphology between a andβ-PP:much more defects existing in theβ-crystalline lamellae,while less defects existing in the a-crystalline lamellae.The defects inβ-PP precursor sheet may act as the favor to form pores during stretching.Theβ-crystalline lamellae induced byβnucleating agent form parallel edge-on lamellar structure which perpendicular to specific crystal face of nucleating agent. This parallel lamellar structure also favors to form pores during stretching.Highβ-crystalline content PP precursor sheet can be prepared by casting the PP melt on the casting roller at about 120℃.The parallel lamellar structure can be obtained by increasing the running speed of the casting roller.And the temperature of the extruding die has a significant effect on the properties of PP films.The effect of technical factors on the morphology and structure of micropore and porosity are investigated,and it is found that,the pore size and porosity increase with increasing of stretching ratio and further increase of stretching ratio may lead to the decrease of the porosity.Separator with high porosity can be obtained by stretching at lower temperature,however,too low temperature may lead to film broken.Uniform film with narrow size distribution can be obtained at low stretching rate.Although higher stretching rate can increase separator yield,large pores will form in the film surface with too high stretching rate.Meanwhile the connectivity of the pores inside the separator is reduced.A newly hydrophobically modified polyacrylamide was synthesized through copolymerization of polyacrylamide and acrylate which were synthesized,and the part of its capability were investigated.The results show that the homemade hydrophobically modified polyacrylamide had good rheology.