碳纳米管表面的RAFT接枝共聚物

首先在碳纳米管表面接枝上可用做RAFT聚合的链转移剂——二硫代碳酸酯,然后用管壁接枝有二硫代碳酸酯的碳纳米管作为链转移剂引发甲基丙烯酸甲酯(MMA)和苯乙烯(St)进行可控的自由基共聚合反应,从而在碳纳米管的管壁接枝上MMA和St共聚物,通过接枝共聚极大地提高了碳纳米管在有机溶剂中的分散性能。并对接枝共聚物的结构进行了较详细的表征。     

两亲性嵌段共聚物PLA-b-PDMAEMA的合成及性能研究

以2-苄基三硫代碳酸酯基乙醇为引发剂,在辛酸亚锡催化下引发丙交酯(LA)开环聚合,合成大分子链转移剂PLA macro-CTA,加入第二单体聚甲基丙烯酸N,N-二甲氨基乙酯(DMAEMA),通过可逆-加成-断裂链转移(RAFT)自由基聚合,得到两亲性嵌段共聚物PLA-b-PDMAEMA。采用核磁共振光谱(1 HNMR和13 CNMR)、红外光谱(FT-IR)及凝胶色谱(GPC)对合成的共聚物化学结构进行表征,并通过接触角测试和热重分析(TGA)对其进行性能测试。结果表明成功合成了嵌段共聚物且分子量分布指数较窄;引入PDMAEMA链段后聚乳酸的热稳定性和亲水性得到提高。     

两亲性三嵌段聚合物的合成与表征及分子自组装行为

以三硫代碳酸(α,α′-二甲基α-″-乙酸)酯为链转移剂,苯乙烯为第一单体,通过RAFT聚合技术合成出大分子链转移剂(PS-CTA);以甲基丙烯酸-N,N-二甲氨基乙酯为第二共聚单体合成出具有不同链长的三嵌段聚合物。GPC对PS-CTA的表征表明:PS-CTA的分子量分别为2100、3500和5000g/m o l,分子量分布约为1.03;NM R表征确定了三嵌段共聚物的结构。三嵌段共聚物在选择性溶剂中可自组装成胶束,通过TEM观察发现胶束呈球形;并且胶束的尺寸随嵌段共聚物分子量的增加而增加。     

三硫代碳酸酯引发的苯乙烯活性自由基光聚合

合成了一种可逆加成-断裂链转移聚合(RAFT)链转移试剂S,S′-二(α,α′-甲基α-″-乙酸)三硫代碳酸酯(TR IT),对以TR IT为链转移剂,苯乙烯(S t)等单体室温下的紫外光引发聚合进行了研究。得到了分布比较窄的PS t(M-w/M-n=1.10~1.14)。研究了S t光聚合过程,ln[M]0/[M]随聚合时间的延长呈线性增加,分子量随转化率也呈线性增长。用FT-IR、NM R等方法对所得聚合物的结构进行了研究,结果表明,聚合物分子链中含有三硫代碳酸酯基。以合成的含有三硫代碳酸酯基的PS t-S-C(=S)-S-PS t为大分子引发剂,在相同的光聚合条件下引发丙烯酸丁酯(BA),得到了分子量分布窄的PS t-PBA-PS t三嵌段共聚物。     

RAFT聚合制备嵌段聚合物对PP基材涂料附着力的改善

合成了RAFT试剂S-1-十二烷基-S’-(α,α’-二甲基-α"-乙酸)三硫代碳酸酯(DDAATB),并以此种RAFT试剂为链转移剂制备聚丙烯酸均聚物,再以此均聚物为大分子链转移剂,制备了聚丙烯酸-b-聚丙烯酸异冰片酯嵌段共聚物(PAA-b-PIBOA)。以制备的丙烯酸酯嵌段共聚物作为附着力促进剂,与UV树脂复配成UV涂料,考察了添加不同质量分数嵌段共聚物的涂料对PP基材的附着能力的改善,并与CPP进行了比较。研究结果表明,制备的丙烯酸酯嵌段共聚物可有效提高涂层对PP基材的粘附性,PIBOA链段分子量越大,效果越明显;将制备的PAA-b-PIBOA为附着力促进剂,分别添加至以聚酯丙烯酸酯、氯化聚醚为主体树脂的涂料配方中,通过附着力性能测试,发现合成的嵌段共聚物PAA-b-PIBOA能有效提高涂层对PP基材的附着力。     

可逆加成-断裂链转移聚合-细乳液聚合法合成聚异戊二烯-b-聚苯乙烯-b-聚甲基丙烯酸甲酯三嵌段共聚物

在水分散的细乳液体系中,以S-正十二烷基-S′-(α,α′-二甲基-α″-乙酸基)三硫代碳酸酯为链转移剂、偶氮二氰基戊酸为引发剂,采用连续加料的方式,依次引发异戊二烯、苯乙烯和甲基丙烯酸甲酯等单体聚合,制备了结构明确的聚异戊二烯-b-聚苯乙烯-b-聚甲基丙烯酸甲酯三嵌段共聚物。采用凝胶渗透色谱、核磁氢谱和差示量热等方法对嵌段聚合物进行了表征。     

PMMA-b-PBMA-b-PNVIm(Bu)BF_4离子液体嵌段聚合物的RAFT合成及表征

以S-十二烷基-S′-(α,α′-二甲基-α″-乙酸)-三硫代碳酸酯为链转移剂,制备了窄分布的聚甲基丙烯酸甲酯(PMMA)大分子链转移剂,用大分子链转移剂来引发第二单体甲基丙烯酸丁酯(BMA)制备了PMMA-b-PBMA二嵌段聚合物。再以二嵌段聚合物为大分子链转移剂引发N-乙烯基咪唑(NVIm)合成PMMA-b-PBMA-b-PNVIm三嵌段聚合物。通过与溴代正丁烷发生季铵化反应并与氟硼酸钠进行阴离子交换得到离子液体嵌段聚合物PMMA-b-PNVIm(Bu)BF_4。运用核磁、红外和凝胶渗透色谱及差示扫描量热等技术对产物的结构、分子量及分子量分布和玻璃化转变温度进行表征。结果表明,嵌段聚合物为PMMA166-b-PBMA145-b-PNVIm144,分子量分布为1.68,合成过程具有活性/可控聚合特征。     

三嵌段聚合离子液体共聚物PMMA-b-PBMA-b-PILs的合成及表征

以偶氮二异丁腈为引发剂、S-十二烷基-S′-(α,α′-二甲基-α″-乙酸)-三硫代碳酸酯为链转移剂,通过可逆加成-断裂链转移自由基聚合(RAFT)方法,制备了聚甲基丙烯酸甲酯PMMA-CTA大分子链转移剂,在大分子链转移剂的作用下,依次引发甲基丙烯酸丁酯(BMA)、甲基丙烯酸二甲胺乙酯(DMAEMA)聚合,合成了相对分子质量分布指数为1.32的三嵌段共聚物——聚甲基丙烯酸甲酯-b-聚甲基丙烯酸丁酯-b-聚甲基丙烯酸二甲胺乙酯(PMMA205-b-PBMA136-b-PDMAEMA128,下标为聚合度),采用核磁共振氢谱仪、傅里叶变换红外光谱仪对共聚物的结构进行了表征。将共聚物与溴代正丁烷发生季铵化反应,再分别与氟硼酸钠(NaBF4)、双三氟甲基磺酰亚胺锂(LiTFSI)进行阴离子交换,得到含有不同反离子(Br-、BF4-、TFSI-)的三嵌段聚合离子液体共聚物PMMA-b-PBMA-b-PILS。电化学交流阻抗方法测定PMMA-b-PBMA-b-PILS的离子电导率为1×10-2S/cm。     

温敏性含氟嵌段聚合物的制备与自组装性能

以丙烯酸六氟丁酯(HFBA)为疏水单体、N-异丙基丙烯酰胺(NIPAM)为亲水单体、偶氮二异丁腈(AIBN)为引发剂、S,S'-二(α,α'-甲基-α″-乙酸)三硫代碳酸酯为链转移剂,采用可逆加成-断裂链转移聚合法(RAFT)合成系列温敏性两亲三嵌段聚合物PNIPAM-PHFBA-PNIPAM,采用透光率法测定其温敏性...     

温敏性嵌段共聚物的可逆加成-断裂链转移法合成及胶束性能EI北大核心CSCD

以N-异丙基丙烯酰胺(NIPAM)与丙烯酸丁酯(BA)为聚合单体,采用可逆加成-断裂链转移(RAFT)聚合,以偶氮二异丁腈(AIBN)为引发剂,三硫代酯(TTC)为链转移试剂制成一系列的温敏性PBA-b-PNIPAM-b-PBA三嵌段共聚物。采用核磁共振表征了共聚物的结构;并采用表面张力仪、分光光度计和动态光散射方法研究了自组装所得胶束的形态和温敏特性,其中所有嵌段聚合物的临界胶束浓度(CMC)均小于1.6×10-3mg/mL,嵌段共聚物具有表面活性;嵌段共聚物具有显著的温敏性,随BA/NIPAM质量比增加其低临界溶解温度(LCST)越低;升高温度胶束粒径先减小后增大,在LCST时有最小值。     

碳纳米管／聚氨酯纳米复合材料的制备及性能

采用可逆加成-断裂链转移(RAFT)聚合方法在碳纳米管表面接枝聚甲基丙烯酸甲酯和聚苯乙烯嵌段共聚物MWNT-P(MMA-b-St),对碳纳米管进行改性。采用直接共混法制备碳纳米管/水性聚氨酯纳米复合材料。通过红外光谱(FT-IR)和透射电镜(TEM)对嵌段共聚物的结构进行了表征。碳纳米管加入对乳液成膜性影响不大。热失重分析(TGA)和力学性能测试结果表明,当改性后的碳纳米管含量为聚氨酯固体份的0.75%时,复合材料的热稳定性、拉伸强度和断裂伸长率均较聚氨酯有所提高。     

Synthesis and characterization of water-soluble multiwalled carbon nanotubes grafted by a thermoresponsive polymer

Water-soluble multiwalled carbon nanotubes (MWNTs) with temperature-responsive shells were successfully prepared by grafting poly (N-isopropylacrylamide) (PNIPAM) from the sidewalls of MWNTs, via surface reversible addition-fragmentation chain transfer (RAFT) polymerization using RAFT agent functionalized MWNTs as the chain transfer agent. Thermogravimetric analysis (TGA) measurements showed that the weight composition of the as-grown PNIPAM polymers on the MWNTs can be well controlled by the feed ratio (in weight) of NIPAM to RAFT agent functionalized MWNTs (MWNT-SC(S)Ph). The MWNT-g-PNIPAM has good solubility in water, chloroform, and tetrahydrofuran (THF). Transmission electron microscope (TEM) and scanning electron microscope (SEM) images also showed that the MWNT-g-PNIPAM was dispersed individually and eventually bonded with the polymer layer by surface RAFT polymerization. The PNIPAM shell is very sensitive to a change of temperature. This method could find potential applications by grafting other functional polymer chains onto MWNTs.     

碳纳米管／PA6纳米复合材料的制备及力学性能

采用RAFT活性聚合反应在碳纳米管表面接枝聚甲基丙烯酸甲酯(二硫代酯化合物作RAFT试剂),并制备了碳纳米管/PA6纳米复合材料。利用FT-IR、TEM、SEM、TGA等测试方法表征接枝聚合物后的碳纳米管,考察了碳纳米管的用量对碳纳米管/PA6纳米复合材料力学性能的影响,并观察了碳纳米管/PA6纳米复合材料冲击断面形貌。结果表明,聚合物接枝到了碳纳米管表面,碳纳米管/PA6纳米复合材料的力学性能明显提高。     

嵌段共聚物修饰多壁碳纳米管

为了改善多壁碳纳米管的分散性,通过丙烯酸和羟基化多壁碳纳米管的酯化反应将双键引入到碳纳米管的表面,同时利用原子转移自由基聚合合成端基为卤素的苯乙烯-b-甲基丙烯酸羟乙酯嵌段共聚物,并通过对双键的加成反应,将嵌段共聚物引入到多壁碳纳米管的表面,实现了碳纳米管的化学修饰。通过FTIR、TGA和TEM技术对产物进行了表征,结果表明:嵌段共聚物通过共价键接枝到碳纳米管表面,其含量为42.9%,平均约277个碳原子接枝一条聚合物链;修饰后的MW CNTs在乙醇中分散良好。     

RAFT-mediated synthesis of cationic poly[(ar-vinylbenzyl)trimethylammonium chloride] brushes for quantitative DNA immobilization

The synthesis of cationic poly[(ar-vinylbenzyl)trimethylammonium chloride)] [poly(VBTAC)] brushes was achieved via reversible addition-fragmentation chain transfer (RAFT) polymerization and used for quantitative DNA immobilization. Initially, silicon surfaces were modified with RAFT chain transfer agent by utilizing an amide reaction involving a silicon wafer modified with allylamine and 4-cyanopentanoic acid dithiobenzoate (CPAD). Poly(VBTAC) brushes were then prepared via RAFT-mediated polymerization from the surface immobilized CPAD. Various characterization techniques including ellipsometry, X-ray photoelectron spectroscopy, grazing angle-Fourier transform infrared spectroscopy, atomic force microscopy and contact-angle goniometer were used to characterize the immobilization of CPAD on the silicon wafer and the subsequent polymer formation. The addition of free CPAD was required for the formation of well-defined polymer brushes, which subsequently resulted in the presence of free polymer chains in solution. The free polymer chains were isolated and used to estimate the molecular weights and polydispersity index of chains attached to the surface. Moreover, from atomic force microscopy and ellipsometry measurements, it was also determined that the density of immobilized DNA on the cationic poly(VBTAC) brushes can be quantitatively controlled by adjusting the solution concentration.     

Surface functionalization of biomaterials by radical polymerization

One effective strategy in the field of biomaterials is to develop biomimetic interfaces to modulate the cell behavior and promote tissue regeneration and surface modification is the best way to obtain biomaterial surfaces with the desired biological functions and properties. Surface radical polymerization offers many advantages compared to other methods, for instance, low cost and simplicity, ability to control the surface chemistry without changing the properties of the bulk materials by introducing high-density graft chains and precisely controlling the location of the chains grafted to the surface, as well as long-term chemical stability of the chains introduced by this method due to the covalent bonding. Because of the precise control of the macromolecules and easy preparation, controlled/living radical polymerization has been widely used to modify biomaterials. There are three main techniques: atom transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP), and reversible radical addition-fragmentation chain transfer (RAFT) polymerization. Some other grafting methods such as plasma-induced polymerization, irradiation-induced polymerization, and photo-induced polymerization also have great potential pertaining to functionalization of biomaterials and tailoring of surface chemistry. This paper summarizes recent advances in the various grafting polymerization methods to enhance the surface properties and biological functions of biomaterials.     

Ruthenium complex containing block copolymer for the enhancement of carbon nanotube photoconductivity

We report the synthesis of a multifunctional block copolymer incorporated with pyrene and ruthenium terpyridyl thiocyanato complex moieties by reversible addition-fragmentation chain transfer polymerization. The pyrene block in the copolymer facilitates the dispersion of multiwalled carbon nanotubes in DMF solution because of the strong π-π interaction between the pyrene moieties and nanotube surface. On the other hand, the ruthenium complexes greatly enhance the photosensitivity of the functionalized nanotubes in the visible region. The photocurrent responses of the nanotubes at different wavelength measured by conductive AFM spectrum strongly agree with the absorption spectrum of the ruthenium complex. The results demonstrate a new and versatile approach in enhancing and fine-tuning the photosensitivity or other opto-electronic properties of carbon nanotubes by multifunctional block copolymers.     

含多芳香环嵌段聚合物PS-b-PAH对碳纳米管的修饰

以芘丁酸为原料通过酯化反应制备了含芘丁单元的苯乙烯基单体,再利用原子转移自由基聚合法（ATRP）合成了分子量可控的嵌段聚合物PS-b-PAH,采用凝胶渗透色谱（GPC）、核磁共振（1H-NMR）等测试手段对产物进行了表征。采用聚合物对碳纳米管表面修饰,比较了聚苯乙烯PS和嵌段聚合物PS-b-PAH修饰碳纳米管后在THF...     

Synthesis and characterization of well-defined polymer brushes grafted from silicon surface via surface reversible addition-fragmentation chain transfer (RAFT) polymerization

Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to prepare polymer brushes grafted onto silicon wafer surface. Novel RAFT agent was prepared and immobilized on the silicon wafer surface. RAFT polymerizations were then conducted from the silicon surface to graft polymer brush to the silicon. Analysis of the polymer brush layers was conducted using ellipsometry, XPS, AFM and contact angle measurements, respectively.