光敏感遥爪聚合物C-PDMAEMA的合成及其性能研究

以香豆素二硫化物(C-S-S-C)/三丁基膦复合体系为链转移剂、甲基丙烯酸-N,N-二甲氨基乙酯(DMAEMA)为单体、偶氮二异丁腈(AIBN)为引发剂制备了末端为香豆素光响应基元的双亲性遥爪聚合物(C-PDMAEMA). 用FTIR, GPC, ¹H NMR等对该聚合物进行了结构表征. 研究表明该遥爪聚合物可直接在水中形成纳米聚集体|且其香豆素端基可在365 和254 nm交替光照下进行可逆光二聚反应. 同时纳米粒度跟踪(Malvern Zetasizer Nano-ZS)、透射电镜(TEM)跟踪结果表明, 随香豆素端基光二聚反应的进行, 聚合物纳米聚集体的粒径逐渐增大|反之, 随着光解二聚反应的进行, 该纳米聚集体的粒径逐渐减小.     

双亲性光敏感遥爪聚合物C-PNIPAAm的合成与性能

以7-羟基-4-甲基香豆素为原料,依次与环氧氯丙烷、二硫化钠反应得一含香豆素基元的二硫化物(C-S-S-C),并以其与三丁基膦复合体系为链转移剂,偶氮二异丁腈(AIBN)为引发剂,N-异丙基丙烯酰胺(NIPAAm)为单体制备了末端为香豆素光响应基元的双亲性遥爪聚合物(C-PNIPAAm).用傅里叶变换红外(FT-IR)光谱、凝胶渗透色谱(GPC)、氢核磁共振(1H-NMR)等对该聚合物进行了结构表征.研究显示该双亲性遥爪聚合物可在水中直接形成胶束,并以荧光素为疏水性客体考察了聚合物胶束的光控释放行为.在波长大于310 nm的紫外光照射下,聚合物链末端的香豆素单元可进行光二聚,胶束结构随之改变,因而所负载的荧光素可得到逐步有效释放.动态激光光散射(DLS)检测显示,光二聚反应使聚合物胶束平均粒径从56.6 nm增大至101.0 nm.     

含香豆素基团超支化星形聚合物的合成与表征

设计并合成了含有香豆素基团的自引发单体, 与2-(2-甲氧基乙氧基)乙基甲基丙烯酸酯(MEO₂MA)进行自缩合乙烯基共聚合后得到超支化聚合物H-PMEO₂MA. 以其作为大分子引发剂, 进行二甲氨基乙基甲基丙烯酸酯(DMAEMA)的原子转移自由基聚合, 合成了具有温度响应性的超支化星形聚合物H-PMEO₂MA-star-PDMAEMA. 将此超支化星形聚合物在水中自组装成胶束后, 利用支化点处香豆素基团的光二聚性能, 在λ=320 nm的紫外光照射下进行香豆素间的光交联反应, 形成核交联胶束. 此核交联胶束在254 nm紫外光照射下则会发生解交联反应. 采用尼罗红作为模型药物, 将其装载到超支化星形聚合物胶束中, 研究了不同条件下的药物释放行为.     

基于原子转移自由基聚合技术的偶氮苯星形液晶聚合物的合成与表征

利用原子转移自由基聚合(ATRP)技术合成了含不同端基取代基的偶氮苯三臂星形侧链液晶聚合物. 均苯三酚与2-溴异丁酰溴通过酯化反应制备三官能团引发剂, 引发偶氮苯单体6-[4-(4-甲氧基苯基偶氮)酚氧基]己基甲基丙烯酸酯(MMAzo)或6-[4-(4-乙氧基苯基偶氮)酚氧基]己基甲基丙烯酸酯(EMAzo)的ATRP反应. 利用核磁共振氢谱(¹H NMR)、凝胶色谱(GPC)、差示扫描量热法(DSC)和偏光显微镜(POM)等手段对星形聚合物进行表征. 星形聚合物的液晶性与相应均聚物相似, 但偶氮苯端基取代基的不同导致星形聚合物的液晶性差别显著. 在紫外/可见光照射下星形聚合物呈现明显的异构化转变.     

α-环糊精修饰型香豆素的设计合成

以环氧氯丙烷为桥接,利用水溶性α-环糊精(α-CD)进行7-羟基-4-甲基香豆素的功能化修饰,得到新型α-环糊精修饰型香豆素衍生物(α-CD-C).用傅里叶变换红外(FT-IR)光谱、氢核磁共振(1H NMR)、液质联用(LC-MS)等对该香豆素衍生物进行了结构表征.紫外光二聚实验表明,该α-环糊精修饰型香豆素可在365 nm光照下进行光二聚反应,且可在随后的254 nm光照下进行解二聚反应;同时通过比较该交替光照下的光二聚反应程度,可知该光二聚反应仅是部分可逆的.     

ARGET ATRP 与ROP 结合制备pH 响应两亲性聚合物分子刷及其自组装研究

结合电子转移活化剂再生-原子转移自由基聚合(ARGET ATRP)和开环聚合(ROP)法合成了一种具有无规疏水/ pH 响应结构的两亲性聚合物分子刷聚(甲基丙烯酸聚丙交酯酯-co-甲基丙烯酸)-b-聚甲基丙烯酸单甲氧基聚乙二醇酯 [P(PLAMA-co-MAA)-b-PPEGMA]. 通过核磁共振氢谱(¹H NMR)和凝胶渗透色谱(GPC)表征了聚合物的结构、分子量及分子量分布. 优化了反应条件并合成出分子量可控、分子量分布窄的聚合产物. 采用动态光散射法(DLS)、扫描电子显微镜(SEM)研究了聚合物分子刷在水溶液中自组装胶束的粒径、形貌及pH 响应行为. P(PLAMA-co-MAA)-b-PPEGMA 自组装形成粒径分布均匀的球形胶束. 且随着溶液pH 值从7 降低至3, 胶束中的PMAA 逐渐去离子化, 溶胀的胶束逐渐收缩, 粒径由200～300 nm 减小至150 nm 左右; 但当pH 值减小到2 以下, 胶束表面电荷量非常小, 胶束聚集, 使得粒径增大.     

光敏感双亲性梳状SMA聚合物的合成及其胶束化

以含香豆素型苯乙烯类光敏单体(coumarin-containing styrene monomer, CS)与苯乙烯(St)、马来酸酐(MA)为反应单体, 以偶氮二异丁腈(AIBN)为引发剂制备了光敏感三元苯乙烯-马来酸酐共聚物(SMA)双亲交替聚合物P(St/CS-alt-MA), 再利用羧酸酐基元与正辛胺的室温胺解反应获得光敏感双亲性梳状聚合物P(St/CS-alt-MAA8). 用傅立叶变换红外光谱(FTIR)、凝胶渗透色谱(GPC)、1H核磁共振(1H-NMR)等对该双亲梳状聚合物进行结构表征. 通过香豆素基元的光二聚作用, 使梳状聚合物溶解在DMSO中进行光照预交联; 非交联与预交联聚合物分别在选择性溶剂中自组装形成胶束; 利用羧酸基元与NaOH的离子化作用改变聚合物胶束的亲疏水性质. 动态激光光散射(DLS)与芘荧光探针实验表明预交联聚合物胶束较非交联胶束粒径大, 负载芘的能力强; 离子化作用使聚合物胶束解离重组成粒径更小的胶束, 但预交联胶束较非交联胶束小, 离子化后胶束疏水微区更加紧密, 负载芘的能力也增大.     

氧化响应性含硒聚己内酯-b-聚磷酸酯三嵌段 聚合物胶束的合成及性能

以聚己内酯为大分子引发剂、异辛酸亚锡为催化剂引发磷酸酯单体2-乙氧基-2-氧-1,3,2-二氧磷酸酯环戊烷(EOP)开环聚合得到二嵌段的聚己内酯-b-聚磷酸酯聚合物PCL-PEEP。以1-(3-二甲氨基丙基)-3-乙基碳二亚胺,4-二甲氨基吡啶为偶合催化体系,以新合成的二羧酸含硒小分子3,3′-硒代二丙酸(Se-DCP)为偶联剂,得到含硒三嵌段聚合物PCL-PEEP-Se-PEEP-PCL,并采用溶剂挥发法制备该聚合物的胶束。通过核磁共振、红外光谱和凝胶渗透色谱对聚合物的结构进行了表征,通过荧光光谱、核磁共振氢谱、动态光散射和透射电镜对聚合物胶束的临界胶束浓度和氧化响应性进行了分析表征,利用噻唑蓝(MTT)比色法评价了聚合物胶束的生物相容性。结果表明:硒元素成功引入到聚合物中;聚合物胶束的临界胶束质量浓度为0.022mg/mL,胶束为平均粒径约91nm的球形;在过氧化氢的氧化条件下,胶束粒径出现不规则变化且球形胶束发生解组装;聚合物胶束具有良好的生物相容性。     

化学酶法合成五嵌段聚合物及其自组装行为的研究

用酶促开环聚合与ATRP方法相结合,制备了聚甲基丙烯酸六氟丁酯-聚己内酯-聚乙二醇-聚己内酯-聚甲基丙烯酸六氟丁酯(PHFMA-b-PCL-b-PEG-b-PCL-b-PHFMA)五嵌段聚合物.首先用Novozym e 435作为催化剂合成了聚己内酯-聚乙二醇-聚己内酯三嵌段聚合物,然后通过端基官能化法合成了大分子引发剂,并用其引发甲基丙烯酸六氟丁酯(HFMA)的ATRP反应,合成了五嵌段聚合物.通过核磁和GPC证明了大分子引发剂和五嵌段共聚物的结构,五嵌段共聚物的GPC分析表明这种合成方法的可行.共聚物胶束的直径和大小通过动态光散射方法和原子力显微镜测试,五嵌段共聚物在水中的的自组装行为也被研究.结果证明胶束是球形,其平均直径为77 nm.聚合物在四氢呋喃中的浓度对聚合物的聚集形貌有很大的影响.     

Y型星形杂臂甲壳型液晶聚合物的合成及其液晶行为研究

通过原子转移自由基聚合(ATRP)与ATRP衍生物化学修饰结合的方法,合成了含一条聚苯乙烯(Ps)臂、两条聚[乙烯基对苯二甲酸二(对甲氧基苯酚)酯](PMPCS)臂的Y型星形杂臂甲壳型液晶聚合物Ps(PMPCS)2.采用核磁共振谱(1H NMR)和凝胶渗透色谱(GPC)手段确定了聚合物的基本结构,所得聚合物为接近单分散...     

Synthesis of star‐shaped poly(n‐butyl acrylate) oligomers with coumarin end groups and their networks for a UV‐tunable viscoelastic material

Solvent‐free isothermal tuning of viscoelasticity of polymer materials is important for an emerging photochemical molding technology and photoreversible adhesives. In this study we designed a four‐armed star‐shaped poly(butyl acrylate, BA) oligomer having four coumarin end groups. The irradiation of UV at the wavelength of 365 nm (UV₃₆₅) to the viscous poly(BA) oligomer under a solvent‐free condition produced a solid network material along with the progress of dimerization reaction with coumarin end groups. The subsequent irradiation of UV at the wavelength of 254 nm (UV₂₅₄) caused dimer dissociation reaction to attain change in the mixing degree of star and network architectures in the material. Moreover, viscoelasticity of the network material was tunable by repetitive UV₃₆₅ and UV₂₅₄ irradiations. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 9–15     

Synthesis and supramolecular self‐assembly of thermosensitive amphiphilic star copolymers based on a hyperbranched polyether core

A novel amphiphilic thermosensitive star copolymer with a hydrophobic hyperbranched poly (3‐ethyl‐3‐(hydroxymethyl)oxetane) (HBPO) core and many hydrophilic poly(2‐(dimethylamino) ethyl methacrylate) (PDMAEMA) arms was synthesized and used as the precursor for the aqueous solution self‐assembly. All the copolymers directly aggregated into core–shell unimolecular micelles (around 10 nm) and size‐controllable large multimolecular micelles (around 100 nm) in water at room temperature, according to pyrene probe fluorescence spectrometry and ¹H NMR, TEM, and DLS measurements. The star copolymers also underwent sharp, thermosensitive phase transitions at a lower critical solution temperature (LCST), which were proved to be originated from the secondary aggregation of the large micelles driven by increasing hydrophobic interaction due to the dehydration of PDMAEMA shells on heating. A quantitative variable temperature NMR analysis method was designed by using potassium hydrogen phthalate as an external standard and displayed great potential to evaluate the LCST transition at the molecular level. The drug loading and temperature‐dependent release properties of HBPO‐star‐PDMAEMA micelles were also investigated by using indomethacin as a model drug. The indomethacin‐loaded micelles displayed a rapid drug release at a temperature around LCST. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 668–681, 2008     

In-situ polymerization at the interfaces of micelles: a "grafting from" method to prepare micelles with mixed coronal chains

Herein we describe a new strategy for producing micelles with mixed coronal chains. This method involves attachment of an atom transfer radical polymerization (ATRP) initiator at the interface of a micelle and preparation of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes at the interface by a "grafting from" method. Poly(ethylene glycol)- block-polystyrene (PEG- b-PS) diblock copolymer was achieved by ATRP. After the sulfonation reaction PS blocks were partly sulfonated. In aqueous solution at low pH the sulfonated block copolymer self-assembled into micelles with PS cores and PEG coronae and sodium 4-styrenesulfonate groups were distributed at the interfaces of the micelles. An ATRP initiator consisting of a quaternary ammonium salt moiety and a 2-bromo-2-methyl propionate moiety was ion exchanged onto the interface of the micelle. ATRP of DMAEMA was initiated at the interface, and micelles with PEG/PDMAEMA mixed coronal chains were prepared by ATRP. The structures of the micelles were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and zeta potential measurements. The size and morphology of the micelles were controlled by pH in aqueous solution. At high pH, PDMAEMA brushes collapse, forming nanodomains on the surface of the micelles. PDMAEMA brushes in the coronae of the micelles could be used as a template for preparation of gold nanoparticles.     

Photo-dimerization characteristics of coumarin pendants within amphiphilic random copolymer micelles

The photo-dimerization characteristics of coumarin pendants within amphiphilic random copolymer micelles in aqueous solution was comprehensively investigated using various selected wavelength light in the UV-Vis-NIR region.The time-dependent photo-dimerization degree(PD) changes in the photo-dimerization experiments showed saturating behaviors with intensity-independent of PDmax values at 28%,44%,92%,85%,36%,35%,32% and 31% for 254,288,320,360,400,500,650 and 900 nm irradiations,respectively.The irradiation experiments at 254 and 288 nm announced the occurring of an asymmetric equilibrium of photo-dimerization and photo-cleavage at the used conditions.Both the alternative irradiation cycles of 360 and 254 nm,650 and 254 nm showed a partially,but evidently reversible photo-dimerization tendency.     

Study of Stimuli-Sensitivities of Amphiphilic Modified Star Poly[N,N-(Dimethylamino)ethyl Methacrylate] and Its Ability of DNA Complexation

Cationic star polymers as drug/gene carriers have attracted increasing attention. Herein, environmental sensitivities and star-shaped architecture were combined into a well-defined gene carrier system, and further amphiphilic modification was conducted. The thermo- and pH-sensitive behaviors of poly[N,N-(dimethyl amino)ethyl methacrylate] (PDMAEMA) star polymers before and after amphiphilic modification in aqueous solutions were investigated. The observed lower critical solution temperature (LCST) increased with increasing arm length due to the increase of hydrophilicity. A significant decrease of the LCSTs with increasing pH and ionic-strength of the solution was found. The incorporation of MMA and BA lipophilic moieties decreased the LCST of the cationic star polymer due to enhanced hydrophobic interaction. As a potential gene carrier, the performance of star polymers on binding DNA was primarily evaluated via particle size, zeta potential, and gel retardation measurements. All the complexes formed stable small particles with diameter of 100～150 nm at N/P ratio higher than 3.0. The electrostatic screening effect and facilitation for the interaction of complexes with cell membrane induced by the incorporation of lipophilic units were expected to enhance the gene transfection efficiency.     

多重响应性超支化星形聚合物的合成与组装以及控制释放研究

含二硫键的自引发单体与2-(2-甲氧基乙氧基)乙基甲基丙烯酸酯(MEO₂MA)进行自缩合乙烯基共聚合得到超支化PMEO₂MA(H-PMEO₂MA). 以它作大分子引发剂, 引发二甲氨基乙基甲基丙烯酸酯(DMAEMA)进行原子转移自由基聚合, 合成了具有温度、pH以及氧化还原多重响应性的超支化星形聚合物H-PMEO₂MA-star-PDMAEMA. 证明了H-PMEO₂MA有低临界溶液温度(LCST); 研究了PDMAEMA 链段的长度和溶液的pH值对超支化星形聚合物的LCST的影响. 当H-PMEO₂MA-star-PDMAEMA水溶液温度从2 ℃升高至室温, H-PMEO₂MA变成疏水性而发生聚集, 形成以H-PMEO₂MA为核, PDMAEMA为壳的胶束. 在胶束形成过程中, 将尼罗红装载到这种聚合物胶束中, 形成释药系统, 研究了pH、氧化还原响应性释药性能.     

结构规整的高密度两亲性接枝聚合物刷的合成及其自组装研究

大分子单体通过两种可控聚合方法, 即开环易位聚合(ROMP)和原子转移自由基聚合(ATRP)的联用, 合成一种新型两亲性接枝聚合物刷. 具有高环张力的降冰片烯单侧链大分子单体norbornene-graft-poly(ε-caprolactone)/Br (PCL- NBE-Br)首先进行ROMP反应, 生成聚合物主链, 每个单体单元上含有一条PCL链和一个溴官能团; 然后用含溴的ROMP聚合物poly(norbornene)-graft-poly(ε-caprolactone)/Br (PCL-PNBE-Br)作为大分子引发剂引发单体2-(dimethyl- amino)ethyl methacrylate)的ATRP反应, 生成结构明确的高密度两亲性接枝聚合物刷poly(norbornene)-graft-poly(ε- caprolactone)/poly(2-(dimethylamino)ethyl methacrylate) (PCL-PNBE-PDMAEMA), 其主链每个单体单元上均含有一条疏水性PCL接枝链和一条亲水性PDMAEMA接枝链. 最后, 研究此类高密度两亲性接枝聚合物刷的自组装行为, 用动态激光光散射(DLS)研究其在混合溶剂(THF/H2O)中的胶束行为, 考察胶束溶液的浓度以及不同长度的亲水性接枝链对胶束尺寸的影响; 利用透射电镜(TEM)观察胶束为球形, 具有类似线团或草莓状的形态.     

Investigation of pH-responsive properties of polymeric micelles with a core-forming block having pendant cyclic ketal groups

In this study, three kinds of amphiphilic block copolymers, termed MPEG-block-PDMMA, MPEG-block-PCPMA, and MPEG-block-PMPMA, which were composed of one hydrophilic monomethoxy poly(ethylene glycol) (MPEG) block and one hydrophobic polyacrylate block bearing pendant six-member cyclic ketal groups, were synthesized by atom transfer radical polymerization (ATRP). These polymers can disperse in aqueous media to self-assemble into micellar aggregates with a spherical core-shell structure with mean diameter below 300 nm. The stimuli-responsiveness of polymeric micelles from MPEG-block-PDMMA was detected by fluorescence-probe technique at pH 3.5 and 37 °C. The effect of chemical architecture and composition of the polymers on the pH-responsive properties of polymeric micelles was also studied. A combination of pH and temperature to trigger release behavior of these polymeric micelles was discussed by comparing the encapsulated molecule release ability under various pH and temperature conditions and analyzing chemical structural changes of the polymer before and after the triggering.     

Preparation of poly(ethylene oxide) star polymers and poly(ethylene oxide)–polystyrene heteroarm star polymers by atom transfer radical polymerization

Poly(ethylene oxide) (PEO) star polymer with a microgel core was prepared by atom transfer radical poylmerization (ATRP) of divinyl benzene (DVB) with mono‐2‐bromoisobutyryl PEO ester as a macroinitiator. Several factors, such as the feed ratio of DVB to the initiator, type of catalysts, and purity of DVB, play important roles during star formation. The crosslinked poly(divinyl benzene) (PDVB) core was further obtained by the hydrolysis of PEO star to remove PEO arms. Size exclusion chromatography (SEC) traces revealed the bare core has a broad molecular weight distribution. PEO–polystyrene (PS) heteroarm star polymer was synthesized through grafting PS from the core of PEO star by another ATRP of styrene (St) because of the presence of initiating groups in the core inherited from PEO star. Characterizations by SEC, ¹H NMR, and DSC revealed the successful preparation of the target star copolymers. Scanning electron microscopy images suggested that PEO–PS heteroarm star can form spherical micelles in water/tetrahydrofuran mixture solvents, which further demonstrated the amphiphilic nature of the star polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2263–2271, 2004