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2002 Volume 20 Issue 2
2002, 20(2): 93-98
Abstract:
According to the present theories of plastic toughening, it is impossible to enhance the toughness, stiffness and/orheat resistance of plastics simultaneously by using rubber. A series of novel nano-rubber particles (UFPR) were introduced,which were prepared through irradiating common rubber lattices and spray drying them. Epoxies toughened with UFPRshowed a much better toughening effect than those with CTBN, and the heat resistance of epoxy was unexpectedly elevated.For polypropylene toughening,UFPR can improve the toughness,stiffness and heat resistance of PP simultaneously.These special toughening effects overcome the deficiencies in rubber toughening technology and are worth further investigating.
According to the present theories of plastic toughening, it is impossible to enhance the toughness, stiffness and/orheat resistance of plastics simultaneously by using rubber. A series of novel nano-rubber particles (UFPR) were introduced,which were prepared through irradiating common rubber lattices and spray drying them. Epoxies toughened with UFPRshowed a much better toughening effect than those with CTBN, and the heat resistance of epoxy was unexpectedly elevated.For polypropylene toughening,UFPR can improve the toughness,stiffness and heat resistance of PP simultaneously.These special toughening effects overcome the deficiencies in rubber toughening technology and are worth further investigating.
2002, 20(2): 99-104
Abstract:
An optically active monomer containing azobenzene moieties with chiral group (s-2-methyl-butyl), 4-[2-(methacryloyloxy)ethyloxy]-4'-(s-2-methyl-1-butyloxycarbonyl) azobenzene(Ml) was synthesized. Polymer (PMl)possessing optical phase conjugated response was obtained by homopolymerzation of the optically active monomer (Ml)using free radical polymerization. The polymer was very soluble in common solvents and good optical quality films could beeasily fabricated by spin coating. The optical phase conjugated responses of the polymer PMI were measured by degenerate four-wave mixing (DFWM).In comparison with polymer containing no chiral group,it was found from the preliminary measurement of photoisomeric change that optical phase conjugated response of the PMI in the long-range order hexagonal symmetry microstructure could be easily controlled by choosing the appropriate polarization direction of the irradiating beams(514.5nm) and the irradiating number,presumably due to the chiral group in the PMI molecular structure.For the case of the polymer investigated here,a chiral group side chain was introduced to increase optical phase conjugated response intensity with different polarization directions of the irradiating beams,which aims originally at searching for a new photoactive material.
An optically active monomer containing azobenzene moieties with chiral group (s-2-methyl-butyl), 4-[2-(methacryloyloxy)ethyloxy]-4'-(s-2-methyl-1-butyloxycarbonyl) azobenzene(Ml) was synthesized. Polymer (PMl)possessing optical phase conjugated response was obtained by homopolymerzation of the optically active monomer (Ml)using free radical polymerization. The polymer was very soluble in common solvents and good optical quality films could beeasily fabricated by spin coating. The optical phase conjugated responses of the polymer PMI were measured by degenerate four-wave mixing (DFWM).In comparison with polymer containing no chiral group,it was found from the preliminary measurement of photoisomeric change that optical phase conjugated response of the PMI in the long-range order hexagonal symmetry microstructure could be easily controlled by choosing the appropriate polarization direction of the irradiating beams(514.5nm) and the irradiating number,presumably due to the chiral group in the PMI molecular structure.For the case of the polymer investigated here,a chiral group side chain was introduced to increase optical phase conjugated response intensity with different polarization directions of the irradiating beams,which aims originally at searching for a new photoactive material.
2002, 20(2): 105-118
Abstract:
Among the inherent drawbacks of conducting polymers are the limited processibility, uneven polydispersity inmolecular weigh and the existence of structure defects, which become the obstacles for many electronic, optical andbiological applications that demand the materials to have well-defined structures and high chemical purity. To solve theseproblems, our research in the last decade or so has focused on the synthesis of electroactive oligomers of well-defined structures, controllable molecular weights,narrow or uniform polydispersity.We have developed a general strategy for the synthesis of such of oligomers based on the theory of non-classical or reactivation chain polymerization.The aniline oligomers with minimum 4 nitrogen atoms and 3 phenylene rings exhibit similar characteristic redox behavior and electroactivity as polyaniline.Electronic conductivity of the oligomers of 7 or 8 aniline units approaches that of polyaniline.Solubility of the oligomers is much improved over that of conventional polyaniline.Various functional groups can be introduced into the oligomers either by proper selection of starting materials or by post-synthesis modifications via common organic reactions.The functionalized oligomers undergo further polymerizations to afford a variety of new electroactive materials,including polyamides,polyimides,polyureas,polyurethanes,polyacrylamides and epoxy polymers.Numerous potential applications,particularly as anticorrosion materials,are discussed for the oligomers and their polymeric derivatives.
Among the inherent drawbacks of conducting polymers are the limited processibility, uneven polydispersity inmolecular weigh and the existence of structure defects, which become the obstacles for many electronic, optical andbiological applications that demand the materials to have well-defined structures and high chemical purity. To solve theseproblems, our research in the last decade or so has focused on the synthesis of electroactive oligomers of well-defined structures, controllable molecular weights,narrow or uniform polydispersity.We have developed a general strategy for the synthesis of such of oligomers based on the theory of non-classical or reactivation chain polymerization.The aniline oligomers with minimum 4 nitrogen atoms and 3 phenylene rings exhibit similar characteristic redox behavior and electroactivity as polyaniline.Electronic conductivity of the oligomers of 7 or 8 aniline units approaches that of polyaniline.Solubility of the oligomers is much improved over that of conventional polyaniline.Various functional groups can be introduced into the oligomers either by proper selection of starting materials or by post-synthesis modifications via common organic reactions.The functionalized oligomers undergo further polymerizations to afford a variety of new electroactive materials,including polyamides,polyimides,polyureas,polyurethanes,polyacrylamides and epoxy polymers.Numerous potential applications,particularly as anticorrosion materials,are discussed for the oligomers and their polymeric derivatives.
2002, 20(2): 119-127
Abstract:
The addition effects of organic small molecular substances N,N'-dicyclohexyl-benzothiazyl-2-sulfenamide(DZ)and 3,9-bis{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2,4, 8, 10-tetraoxaspiro [5,5]-un-decane (AO-80) on the dynamic mechanical properties of chlorinated polyethylene (CPE), chlorinated polypropylene (CPP),acrylate rubber (ACM) and their blends were investigated. In the case of compatible systems such as CPE/DZ and ACM/AO-80, the height of the loss tangent(tanδ)peak of a matrix polymer (CPE or ACM) increases,and its peak position shifts to a higher temperature with the addition of DZ or AO-80.By contrast,for incompatible CPE/AO-80,a novel transition appeared above the glass transition temperature of CPE.This additional transition was assigned to dissociation of the intermolecular hydrogen bond between the α-hydrogen of CPE and the hydroxyl groups of AO-80 within the AO-80-rich domain.This will provide a new concept for developing damping material.However,the minimum value between two tan δ peaks is lower.It was found that the temperature dependence of tan δcould be improved by adding chlorinated paraffin (CP) or ACM to CPE/AO-80.In addition,another termary system of ACM/CPP with more AO-80 was found to be a very good self-adhesive damping material because of the appearance of a novel transition due to an interfacial layer of ACM/CPP.
The addition effects of organic small molecular substances N,N'-dicyclohexyl-benzothiazyl-2-sulfenamide(DZ)and 3,9-bis{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2,4, 8, 10-tetraoxaspiro [5,5]-un-decane (AO-80) on the dynamic mechanical properties of chlorinated polyethylene (CPE), chlorinated polypropylene (CPP),acrylate rubber (ACM) and their blends were investigated. In the case of compatible systems such as CPE/DZ and ACM/AO-80, the height of the loss tangent(tanδ)peak of a matrix polymer (CPE or ACM) increases,and its peak position shifts to a higher temperature with the addition of DZ or AO-80.By contrast,for incompatible CPE/AO-80,a novel transition appeared above the glass transition temperature of CPE.This additional transition was assigned to dissociation of the intermolecular hydrogen bond between the α-hydrogen of CPE and the hydroxyl groups of AO-80 within the AO-80-rich domain.This will provide a new concept for developing damping material.However,the minimum value between two tan δ peaks is lower.It was found that the temperature dependence of tan δcould be improved by adding chlorinated paraffin (CP) or ACM to CPE/AO-80.In addition,another termary system of ACM/CPP with more AO-80 was found to be a very good self-adhesive damping material because of the appearance of a novel transition due to an interfacial layer of ACM/CPP.
2002, 20(2): 129-136
Abstract:
New water soluble and photocrosslinkable prepolymers colltaining acrylate and quaternary ammonium salt groupswere synthesized from epoxy phenolic resin via ring-opening reaction with acrylic acid and with aqueous solution oftriethylamine hydrochloride successively. The second reaction needs no phase transfer catalyst to accelerate, since theproduct formed can act as a phase transfer catalyst. The prepolymer obtained contains both photocrosslinkable acrylategroups and hydrophilic quaternary ammonium salt groups.Optimum conditions for these reactions were studied.The photosensitivity of the prepolymer was also investigated.The effects of different photoinitiators,different crosslinkable diluent monomers and amine accelerator on the photosensitivity of the prepolymer were compared.The photoinitiator of hydrogen abstraction type is still effective without using amine or alcohol as accelerator,because the prepolymer contains αH beside the OH groups formed in the ring-opening reactions.
New water soluble and photocrosslinkable prepolymers colltaining acrylate and quaternary ammonium salt groupswere synthesized from epoxy phenolic resin via ring-opening reaction with acrylic acid and with aqueous solution oftriethylamine hydrochloride successively. The second reaction needs no phase transfer catalyst to accelerate, since theproduct formed can act as a phase transfer catalyst. The prepolymer obtained contains both photocrosslinkable acrylategroups and hydrophilic quaternary ammonium salt groups.Optimum conditions for these reactions were studied.The photosensitivity of the prepolymer was also investigated.The effects of different photoinitiators,different crosslinkable diluent monomers and amine accelerator on the photosensitivity of the prepolymer were compared.The photoinitiator of hydrogen abstraction type is still effective without using amine or alcohol as accelerator,because the prepolymer contains αH beside the OH groups formed in the ring-opening reactions.
2002, 20(2): 137-142
Abstract:
Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amountof hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750.The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of 0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility in water.It was shown by experimental measurement at 30.3±0.1℃ that the surface tension of the aqueous solution of the highest substituted FPVA decreased to 16.6 mN/m at a higher concentration,e.g. about 0.1 g/mL.Obviously,macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface,because the hydrophobic perfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants.The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed.
Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amountof hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750.The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of 0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility in water.It was shown by experimental measurement at 30.3±0.1℃ that the surface tension of the aqueous solution of the highest substituted FPVA decreased to 16.6 mN/m at a higher concentration,e.g. about 0.1 g/mL.Obviously,macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface,because the hydrophobic perfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants.The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed.
2002, 20(2): 143-154
Abstract:
Crystallization in polymer systems actually is a process that transfers the entangled melts into a semi-crystallinelayered structure. Whether or not a chain disentangles may result in different crystallization mechanism. When compared tothe crystal thickness (dc), the volume occupied by the chain in the melt, i.e., the radius of gyration (Rg), plays a veryimportant role in polymer crystallization. When dc≤Rg, crystallization does not necessitate a chain disentangling. The entanglements are just shifted into the amorphous regions.However,as dc>Rg,i.e., as the crystal thickness gets larger than the radius of gyration of the chain in the melt,it becomes necessary for a chain to disentangle.Then a change of crystallization mechanism occurs.Such change has been experimentally observed in the crystallization of poly(1-butene).A change in the crystal morphologies from spherulite to quadrangle,is seen via PLM,as crystallization temperatures increase.Even more,such a change is molecular weight dependent,and shifts to lower temperature as molecular weight decreases.There exists a jump of crystal thickness and crystallinity associated with morphological change,as seen via SAXS.A change of crystallization kinetics and crystallinity is further evidenced via dilatometry.The unique feature of plb crystallization has been discussed based on the radius of gyration of chain in the melt(Rg),and very good agreement is obtained.
Crystallization in polymer systems actually is a process that transfers the entangled melts into a semi-crystallinelayered structure. Whether or not a chain disentangles may result in different crystallization mechanism. When compared tothe crystal thickness (dc), the volume occupied by the chain in the melt, i.e., the radius of gyration (Rg), plays a veryimportant role in polymer crystallization. When dc≤Rg, crystallization does not necessitate a chain disentangling. The entanglements are just shifted into the amorphous regions.However,as dc>Rg,i.e., as the crystal thickness gets larger than the radius of gyration of the chain in the melt,it becomes necessary for a chain to disentangle.Then a change of crystallization mechanism occurs.Such change has been experimentally observed in the crystallization of poly(1-butene).A change in the crystal morphologies from spherulite to quadrangle,is seen via PLM,as crystallization temperatures increase.Even more,such a change is molecular weight dependent,and shifts to lower temperature as molecular weight decreases.There exists a jump of crystal thickness and crystallinity associated with morphological change,as seen via SAXS.A change of crystallization kinetics and crystallinity is further evidenced via dilatometry.The unique feature of plb crystallization has been discussed based on the radius of gyration of chain in the melt(Rg),and very good agreement is obtained.
2002, 20(2): 155-159
Abstract:
The liquid crystallinity of poly(N-vinylcarbazole) was studied by using powder X-ray diffraction, polarized opticalmicroscopy, and differential scanning calorimetry. The results show that the lower molecular weight fractions of this polymerdo not form a liquid crystalline phase, while the samples of sufficiently high molecular weight do form a mesophase attemperatures above the glass transition. The lowest value of the degree of polymerization for PVK to form a stable liquid crystalline phase was found to be in the range of 150 to 200,significantly higher than the value of 50 for most conventional side chain liquid crystalline polymers.
The liquid crystallinity of poly(N-vinylcarbazole) was studied by using powder X-ray diffraction, polarized opticalmicroscopy, and differential scanning calorimetry. The results show that the lower molecular weight fractions of this polymerdo not form a liquid crystalline phase, while the samples of sufficiently high molecular weight do form a mesophase attemperatures above the glass transition. The lowest value of the degree of polymerization for PVK to form a stable liquid crystalline phase was found to be in the range of 150 to 200,significantly higher than the value of 50 for most conventional side chain liquid crystalline polymers.
2002, 20(2): 161-170
Abstract:
The mechanism of tensile deformation in semi-crystalline polymers was studied based on true stress-strain curvesobtained with the aid of a video-controlled tensile set-up. The deformation is affected by both the crystalline and theamorphous phases. However, the relative weights of the two portions change with the deformation stage. At low deformations the coupling and coarse slips of the crystalline blocks dominate the mechanical properties, which allows the system to maintain a homogeneous strain distribution in the sample.As the stretching increases,at a critical strain the force generated from entangled fluid portions reaches a critical value to destroy the crystallites.The dominant deformation mechanism then changes into a disaggregation-recrystallization process.
The mechanism of tensile deformation in semi-crystalline polymers was studied based on true stress-strain curvesobtained with the aid of a video-controlled tensile set-up. The deformation is affected by both the crystalline and theamorphous phases. However, the relative weights of the two portions change with the deformation stage. At low deformations the coupling and coarse slips of the crystalline blocks dominate the mechanical properties, which allows the system to maintain a homogeneous strain distribution in the sample.As the stretching increases,at a critical strain the force generated from entangled fluid portions reaches a critical value to destroy the crystallites.The dominant deformation mechanism then changes into a disaggregation-recrystallization process.
2002, 20(2): 171-175
Abstract:
Poly(methyl acrylate)-b-poly(5,6-benzo-2-methylene-1, 3-dioxepane) (PMA-b-PBMDO) was synthesized by two-step atom transfer radical polymerization (ATRP). Firstly, ATRP of methyl acrylate (MA) was realized using ethyl α-bromobutyrate (EBrB) as initiator in the presence of CuBr/2,2'-bipyridine. After isolation, poly(methyl acrylate) withterminal bromine (PMA-Br) was synthesized. Secondly, the resulting PMA-Br was used as a macromolecular initiator in theATRP of BMDO. The Structure of block copolymer was characterized by 1H-NMR spectroscopy.Molecular weight and molecular weight distribution were determined on a gel permeation chromatograph(GPC).
Poly(methyl acrylate)-b-poly(5,6-benzo-2-methylene-1, 3-dioxepane) (PMA-b-PBMDO) was synthesized by two-step atom transfer radical polymerization (ATRP). Firstly, ATRP of methyl acrylate (MA) was realized using ethyl α-bromobutyrate (EBrB) as initiator in the presence of CuBr/2,2'-bipyridine. After isolation, poly(methyl acrylate) withterminal bromine (PMA-Br) was synthesized. Secondly, the resulting PMA-Br was used as a macromolecular initiator in theATRP of BMDO. The Structure of block copolymer was characterized by 1H-NMR spectroscopy.Molecular weight and molecular weight distribution were determined on a gel permeation chromatograph(GPC).
2002, 20(2): 177-180
Abstract:
A route was proposed to synthesize 3-benryl-glyceric acid (3-BGA) as an important intermediate for the synthesis ofa novel six-membered cyclic ester monomer - 3-benzyloxymethyl-1,4-dioxane-2,5-dione (3-BMG). According to this route,3-BGA was obtained from ring-opening reaction of benzyl alcohol with methyl glycidate, which was prepared from theepoxidation of methyl acrylate using sodium hypochlorite as the oxidant.
A route was proposed to synthesize 3-benryl-glyceric acid (3-BGA) as an important intermediate for the synthesis ofa novel six-membered cyclic ester monomer - 3-benzyloxymethyl-1,4-dioxane-2,5-dione (3-BMG). According to this route,3-BGA was obtained from ring-opening reaction of benzyl alcohol with methyl glycidate, which was prepared from theepoxidation of methyl acrylate using sodium hypochlorite as the oxidant.
