北京大学高分子辐射化学13

辐射交联辐射降解•气体生成和不饱和度的变化•氧化反应•异构化和歧化反应RadiationeffectofpolymerNineRadiationeffectofpolymerPolymerRadiationRadicalsMonomerCrosslinkingGraftingDegradationRadiationcrosslinking°radationDefinitiononradiationcrosslinking°radationThecharacteristicsofradiationcrosslinkingThemechanismofradiationcrosslinkingreactionCharlesby-PinnerequationFortifiedradiationcrosslinkingRadiationdegradationApplicationonradiationcrosslinking°radationDefinitiononradiationcrosslinking°radation辐射交联是通过射线引发聚合物线性分子以化学键相连使分子量增加，随着交联键的增多逐渐形成区域网状结构，最终形成整体网状结构，成为不溶、不熔的凝胶；辐射降解是使聚合物分子主链断裂，分子量变小，最终形成较小聚合体。辐射交联与降解是同时发生的，但总有一方面是主要的，决定的因素是聚合物单元化学组成和结构。聚合物辐射交联动态示意图Radiation-crosslinkingtypedpolymers聚乙烯,氯化聚乙烯,氯磺化聚乙烯,聚丙烯,聚丙烯酰胺,聚丙烯酸酯(甲酯、乙酯等),聚丙烯腈,聚氟乙烯,聚氯乙烯,聚乙烯基醚，聚醋酸乙烯酯，聚N-乙烯基吡咯烷酮,聚苯乙烯,聚氧乙烯,聚苯二甲酸乙酯,天然橡胶,聚丁二烯,丁二烯-苯乙烯共聚物,乙丙共聚物,聚异戊二烯,丁二烯-丙烯腈共聚物,聚氯丁二烯,聚亚胺,聚己内酰胺,聚硅氧烷，聚二甲基硅氧烷，聚二苯基硅氧烷对乙烯基类聚合物，在结构单元的主链碳原子上的氢无取代或只有一元取代的，以交联为主，但PVA例外。Radiation-degradationtypedpolymers聚乙烯醇,聚异丁烯,聚偏氯乙烯,聚四氟乙烯,聚三氟氯乙烯,聚甲基丙烯酰胺,聚甲基丙烯酸,聚甲基丙烯腈,聚甲基丙烯酸甲酯,丁基橡胶,纤维素,醋酸纤维,硝酸纤维对乙烯基类聚合物，在结构单元的主链碳原子上的两个氢皆被取代，则该聚合物以降解为主。天然高分子多为降解型聚合物。从交联G值，G(x)与降解G值,G(s)的定量关系考虑，一般认为G(x)4G(s)者为辐射交联型聚合物，反之为辐射降解型聚合物。Thecharacteristicsofradiationcrosslinking凝胶含量gelfraction弹性模量modulusofelasticity结晶度crystallinity聚合物交联以后一般结晶度下降。溶胀行为swellingbehavior凝胶强度gelstrength形貌morphologyGelfractionGelfraction(%)=Wg/Wo×100Gelationdose回流法Gelfraction0102030405060708036384042444648505254565860t/hGelFraction/%6080100120140160180200Swelling(mwater/mgel)Fig.SwellingkineticsofCM-chitosanhydrogel(preparefrom15%aqueoussolutionat40kGy)RadiationcrosslinkingofCM-chitosan0204060801000510152025303540abcGelFraction/%Dose/kGy12%CM-chitosan15%CM-chitosan18%CM-chitosanModulusofelasticity(E)cMRTE/3—聚合物密度R—气体常数T—绝对温度随着交联度的增加，弹性模量随之增加。测定:万能材料拉力试验机，流变仪GelstrengthofthehydrogelsThehydrogelwascutintocylinderswitha15mmdiameterand20mmheightfortesting.Gelstrengthwasmeasuredby75%compressionanddecompressionofgelsamplesbetweentheplatesofaStrograph-R1MaterialTesterwithacrossheadspeedof50mm/min.MaolinZhai,CarbohydratePolymers,2004,58(1):35-39.Gelsamplesweredriedtoconstantweightat50oCinavacuumovenandthenwereimmersedindistilledwatertobeswollen.Theswellingratio(R)(basedonswellingkinetics)andequilibriumdegreeofswelling(EDS)(swellingcapacity)werecalculatedasfollows,respectively:R(%)=Wt/W0100EDS(%)=We/W0100whereW0isinitialmassofdriedhydrogel;WtandWearethemassesoftheswollenhydrogelsattimetandatequilibrium,respectively.Swellingbehaviorofpolymer-basedhydrogels020040060050010001500200025003000350020%CMC20%CMC/5%AC20%CMC/10%ACDegreeofswelling(%)Time(min)Fig.SwellingdynamicsofCMC/AChybridhydrogels(25kGy)Swellingbehaviorofpolymer-basedhydrogelsQiuJingyi,CarbohydratePolymer,2007,70:236-242.Fig.EDSofCMC/AChybridhydrogels.Swellingbehaviorofpolymer-basedhydrogels0510152025303540450100002000030000400005000060000EDS(%)Dose(kGy)20%CMC20%CMC/5%AC20%CMC/10%ACStimuli-responseswellingbehaviorofpolymer-basedhydrogelsMaolinZhai,CarbohydratePolymers,2004,58(1):35-39.H3COH2CCH2NCH3CH2OCH3+1-CnH2n+1BrCacetoneH3COH2CCH2N+CH2OCH3CH3CnH2n+1Br-TAA++PEGDMAcross-linkerirradiationwaterTAA+TAA+TAA+TAA+Br-Br-Br-Br-amphiphilicgelsDMAEMAn=2,MEDABn=4,MBDABn=6,MHDABn=8,MODABn=12,MDDABDMAEMA的衍生物聚电解质两亲分子特异性溶胀Stimuli-responseswellingbehaviorofpolymer-basedhydrogelsXuLing,JournalofPolymerScience,PartA:PolymerChemistry2008,46:473-480.LiCancan,Polymer,2009,50:4888-4894.PMADAB凝胶的形貌a-PDMAEMAb-PMBDABc-PMODABd-PMDDABPMADAB凝胶(n≤6):多孔状的细胞结构；PMADAB凝胶(n≥8):聚集体结构(疏水作用和离子对）PMADAB凝胶的溶胀动力学04008001200160020000306090120150180210EDSTime(min)a030060090012001500180021000.00.51.01.52.00.00.10.20.30.40.50.6EDSEDSTime(min)b●-PDMAEMA○-PMEDAB◆-PMBDAB◇-PMHDAB■-PMODAB□-PMDDAB过溶胀PMADAB凝胶（n≤6）的溶胀度比PDMAEMA凝胶大，聚电解质凝胶的渗透压大和静电斥力；PMADAB凝胶（n≥8）的溶胀度比PDMAEMA凝胶的小，因其聚集体结构（疏水作用和离子对）；PMADAB凝胶的溶胀度随着链长的增加而下降，是因为疏水作用增强；PDMAEMA凝胶在水中存在过溶胀。2030405060700.150.200.250.30020406080100120140EDSEDSTemperature(oC)bPMADAB凝胶的温度刺激响应性203040506070050100150200250020406080EDSEDSTemperature(oC)a●-PDMAEMA○-PMEDAB◆-PMBDAB◇-PMHDAB■-PMODAB□-PMDDABPMADAB凝胶（n≤6）不具有温敏性，阳离子聚电解质凝胶具有强的亲水性，疏水作用相对较弱；PMADAB凝胶（n≥8）具有UCST，与PDMAEMA凝胶相反的温敏性，高温下疏水基团和亲水基团的混合，由不均质到均一体系的相转变所致；PMDDAB凝胶相转变温度较PMODAB凝胶低，因为溶胀仅发生在表面。(a)(b)PMADAB凝胶的离子刺激响应性■-PMODAB□-PMDDAB1E-41E-30.010.110501001502002500255075100EDS[NaCl](molL-1)aEDS●-PDMAEMA○-PMEDAB◆-PMBDAB◇-PMHDABPMADAB凝胶(n≤6): 聚电解质效应；PMADAB凝胶(n≥8):反聚电解质效应，NaCl的加入对离子对的破坏；PMDDAB凝胶最大溶胀度较PMODAB凝胶出现在更低的浓度，因为溶胀仅发生在表面。1E-51E-41E-30.010.110.160.170.180.190.200.21020406080100EDS[NaCl](molL-1)bEDS(a)(b)gel[“free”Br-]/[totalBr-](%)H2O2×10-3MNaClsolution5×10-3MNaClsolutionPMBDAB30.137.943.1PMODAB2.444.4PMDDAB0.47.5[“free”Br-]:theconcentrationofBr-ionswhichdonotformionpairswithtetra-ammoniumcations.[totalBr-]:theconcentrationofBr-ionsconsistoffreeBr-andthatformionpairswithtetra-ammoniumcations.“M”isabbreviatedformolL-1.离子对的形成—Br-选择电极PP･H2O･OHHe++++P･OHorHP･+H2OorH2IrradiationIrradiationDirectEffectIndirectEffectP･P-PP･+crosslinkingThemechanismofradiationcrosslinkingreaction固态辐照水凝胶Themechanismofradiationcrosslinkingreaction多数学者认为辐射交联以自