Controlled surface nanotopography and oxygen plasma treatment of PEEK to improve cellular response

Poly(aryl-ether-ether-ketone) (PEEK) is a semi crystalline polymer which exhibits properties that make it an attractive choice for use as an implant material. It displays natural radiolucency, and MRI compatibility, as well as good chemical and sterilization resistance, both of which make it of particular interest in orthopaedic implants. However, PEEK has demonstrated poor cellular adhesion both in vitro and in vivo. This is problematic as implant surfaces that do not develop a layer of adhesive cells are at risk of undergoing fibrous encapsulation, which in turn leads to lack of a strong interface between the implant device and the patient tissue, which can in turn lead to failure of the implant and revision surgery . As incorporating nanotopography into a polymer surface has been demonstrated to be able to direct the differentiation behaviour of stem cells, a possible solution to PEEKs underlying issues with poor cellular response would be to incorporate specific nanoscale topography into the material surface through injection moulding, and then analysing if this is a viable method for addressing PEEKs issues with cellular response. In addition to nanoscale topography, the experimental PEEK surfaces were treated with oxygen plasma to address the underlying cytophobicity of the material. As this type of treatment has been documented to be capable of etching the PEEK surface, experiments were carried out to quantify the effect of this treatment, both on the ability of cells to adhere to the PEEK surface, as well as the effect it has upon the nanotopography present at the PEEK surface. The results demonstrated that there were a range of plasma treatments which would significantly improve the ability of cells to adhere to the PEEK surface without causing unacceptable damage to the nanotopography. Three different types of cells with osteogenic capacity were tested with the PEEK surfaces to gauge the ability of the topography to alter their behaviour: SAOS-2, osteoprogenitors and 271+ MSCs. Due to PEEKs material properties (it is non transparent, exhibits birefringence and is strongly autofluorescent) a number of histological techniques were used to investigate a number of different stages that take place in osteogenesis. The different cell types did display slightly different responses to the topographies. The SAOS-2 cells cultured on surfaces that had been plasma treated for 2 minutes at 200W had statistically significantly higher levels of von Kossa staining on the NSQ surface compared to the planar surface, and the same experiment employing alizarin red staining, showed a statistically significantly lower level of staining on the SQ surface compared to the planar surface. Using primary osteoprogenitor cells designed to look into if whether or not the presence of nanotopography effected the osteogenic response of these cells, we saw a lack of statistically significant difference produced by the surfaces investigated. By utilising HRP based immunostaining, we were able to investigate, in a quantitative fashion, the production of the two osteogenic markers osteopontin and osteocalcin by cells. When stained for osteocalcin, the SQ nanotopography had total percentage of the surface with stained material, average area and average perimeter all statistically significantly lower than the planar surface. For the cells that were stained for osteopontin, the SQ nanotopgraphy had a total percentage of the surface with stained material, average area and average perimeter all highly statistically significantly lower than those of the planar surface. Additionally, for this marker the NSQ nanotopography had average areas and average perimeters that were highly significantly higher than those of the planar surface. There were no significant differences for any of the values investigated for the 271+ MSC’s When plasma treatment was varied, the SAOS-2 cells demonstrated an overall trend i.e. increasing the energy of plasma treatment in turn leads to an increase in the overall percentage of staining. A similar experiment employing stem cells isolated from human bone marrow instead of SAOS-2 cells showed that for polycarbonate surfaces , used as a control, mineralization is statistically significantly higher on the NSQ nanopattern compared to the planar surface, whereas on the PEEK surfaces we observe the opposite trend i.e. the NSQ nanotopography having a statistically significantly lower amount of mineralization compared to the planar surface at the 200W 2min and 30W 1min plasma treatments. The standout trend from the PEEK results in this experiment was that the statistically significant differences on the PEEK substrates were clustered around the lower energy plasma treatments, which could suggest that the plasma treatment disrupted a function of the nanotopograhy which is why, as the energy increases, there are less statistically significant differences between the NSQ nanotopography and the Planar surface This thesis documents the response of a number of different types of cells to specific nanoscale topographies incorporated into the PEEK surface which had been treated with oxygen plasma. It outlines the development of a number of histological methods which measure different aspects of osteogenesis, and were selected to both work with PEEK, and produce quantitative results through the use of Cell Profiler. The methods that have been employed in this body of work would be of interest to other researchers working with this material, as well as those working with similarly autofluorescent materials.

Preparation and catalytic studies of palladium nanoparticles stabilized by dendritic phosphine ligand-functionalized silica

Silica is a prominently utilized heterogeneous metal catalyst support. Functionalization of the silica with poly(ether imine) based dendritic phosphine ligand was conducted, in order to assess the efficacy of the dendritic phosphine in reactions facilitated by a silica supported metal catalyst. The phosphinated poly(ether imine) (PETIM) dendritic ligand was bound covalently to the functionalized silica. For this purpose, the phosphinated dendritic ligand containing an amine at the focal point was synthesized initially. Complexation of the dendritic phosphine functionalized silica with Pd(COD)Cl-2 yielded Pd(II) complex, which was reduced subsequently to Pd(0), by conditioning with EtOH. The Pd metal nanoparticle thus formed was characterized by physical methods, and the spherical nanoparticles were found to have >85% size distribution between 2 nm and 4 nm. The metal nanoparticle was tested as a hydrogenation catalyst of olefins. The catalyst could be recovered and recycled more than 10 times, without a loss in the catalytic efficiency.

A new microscopic insight into membrane penetration and reorganization by PETIM dendrimers

Dendrimers are highly branched polymeric nanoparticles whose structure and topology, largely, have determined their efficacy in a wide range of studies performed so far. An area of immense interest is their potential as drug and gene delivery vectors. Realizing this potential, depending on the nature of cell surface-dendrimer interactions, here we report controlled model membrane penetration and reorganization, using a model supported lipid bilayer and poly(ether imine) (PETIM) dendrimers of two generations. By systematically varying the areal density of the lipid bilayers, we provide a microscopic insight, through a combination of high resolution scattering, atomic force microscopy and atomistic molecular dynamics simulations, into the mechanism of PETIM dendrimer membrane penetration, pore formation and membrane re-organization induced by such interactions. Our work represents the first systematic observation of a regular barrel-like membrane spanning pore formation by dendrimers, tunable through lipid bilayer packing, without membrane disruption.

Desenvolvimento de membranas de poli(éter imida) sultonada para a permeacão de gases

A busca por membranas com propriedades adequadas a separação de gases em escala industrial tem levado a modificação e sIntese de polImeros de engenharia, com objetivo de obter membranas com propriedades adequadas. Uma das modificaçoes que tem se apresentado promissora é a inserção de grupos sulfônicos em polImeros comerciais. Espera-se que o polImero sulfonado apresente um aumento na permeação de gases polares, em relação a gases apolares, devido a sua estrutura mais polar e flexIvel. Neste contexto, o objetivo do presente trabalho é a sIntese e caracterização de membranas de poli(éter imida) sulfonada para a permeação de gases. Um planejamento experimental foi desenvolvido, em diferentes condiçoes reacionais de temperatura, tempo e excesso de um dos reagentes (ácido acético), para a sIntese de poli(éter imida) sulfonada (SPEI). Através deste planejamento, constatou-se que as variáveis que mais influenciam o grau de sulfonação são a temperatura e o tempo. O polImero com o maior grau de sulfonação, determinado por capacidade de troca iônica (IEC= 92 mEq H+/g), foi utilizado para o preparo da membrana de SPEI, obtida pela técnica de inversão de fase por evaporação do solvente, utilizando-se clorofórmio como solvente. Este filme foi caracterizado a partir das seguintes análises: espectroscopia de infravermelho (FTIR), calorimetria diferencial de varredura (DSC), análise termogravimétrica (TGA) e microscopia eletrônica de varredura (MEV), a fim de avaliar a influência da inserção do grupo sulfônico na matriz polimérica. O espectro de infravermelho de SPEI apresentou bandas relacionadas as vibraçoes assimétricas em 1240 cm-1 (ligação O=S=O), ligação simétrica em 1171 cm-1 (O=S=O) e ligação S-O entre 1010-1024 cm-1. Isto indica a presença de grupos sulfônicos. A análise de DSC foi realizada entre 150-250C. Nesta faixa, não foram observadas alteraçoes na temperatura de transição vItrea (Tg) do polImero modificado (217C). Acredita-se que a decomposição do grupo sulfona aconteça antes da temperatura atingir o Tg do polImero. Esta suposição é confirmada na análise de TGA. As imagens de MEV mostraram que foram obtidos filmes livres de poros e defeitos. A membrana da SPEI foi utilizada no ensaio de permeaçao dos gases 02, N2 e C02, a fim de determinar a permeabilidade e seletividade da membrana. As permeabilidades encontradas para o gas oxigênio foram de 0,76 barrer para a PEI e 0,46 barrer para a SPEI. A seletividade do dióxido de carbono em relaçao ao oxigênio aumentou de 3,5, na membrana de PEI, para 4,83, na membrana de SPEI. Em relaçao ao nitrogênio, as permeabilidades medidas foram 0,064 barrer e 0,043 barrer, para a PEI e para a SPEI, respectivamente, enquanto a seletividade em relaçao ao C02 aumentou de 41,1 para 55,5. Estes resultados indicam que o efeito de sorçao predominou devido ao aumento das interaçöes moleculares, reduzindo assim o volume livre, o que tornou a membrana sulfonada mais compacta, com permeabilidade menor e maior seletividade. Estes resultados corroboram com a premissa de que a sulfonaçao é um processo promissor para o desenvolvimento de membranas mais eficientes.

酚酞型聚醚砜的化学改性及其性能研究

酚酞型聚醚砜（C-PES）是一种综合性能优异的工程塑料和功能材料，具有良好的成膜性、机械性能、热稳定性、化学稳定性和可加工性等。作为一种高性能的膜材料，酚酞型聚醚砜已被广泛的用于气体分离和水处理等领域。酚酞型聚醚砜侧链上含有可修饰的酯基，可通过各种方法，引入功能基团，对其进行化学改性，从而改善C-PES的各种性能，并扩展其应用领域。本论文设计制备了含有烷基、芳基、胺基以及磺酸基等功能基团的新型酚酞型聚醚砜材料，并对其性质进行了深入的研究： 1．通过各种基团修饰的二酚单体和二氯二苯砜的缩聚，合成了新型的含有不同酞侧基的Cardo型聚醚砜高分子材料，并对其性能进行了详细的研究。结果表明，所有聚合物都表现出极好的溶解性、耐热稳定性、成膜性、力学性能和气体分离性能；通过在酞侧基上引入了大体积的对叔丁基苯基，大大改善了材料的透气性和氧氮分离选择性；通过引入仲胺基，增大了聚合物链间作用力，从而提高了气体的分离选择性。此外，我们还对不同基团的引入对聚合物各种性能的影响作了详细的探讨，着重研究了聚合物的结构－性能关系。 2．利用含有胺基的双酚单体PPH-NH2、PPH和二氯二苯砜的共聚反应，成功合成了含有胺基的Cardo型聚醚砜高分子材料(PES-NH2)，并对材料的各种性质进行了表征。结果表明，由于胺基的引入，酚酞型聚醚砜的亲水性得到了大幅度的提高。 3．利用含胺基的Cardo双酚和磺化二氯二苯砜在碳酸钾作用下的缩聚反应，成功合成了含胺基的磺化Cardo型聚醚砜 (SPES-NH2)，并用于制备反渗透复合膜。通过优化制膜条件，我们利用界面聚合的方法成功制备了高水通量的TMC/ MPDA/SPES-NH2反渗透复合膜，并对复合膜的性能和结构进行了研究，重点讨论了膜的性能和结构、形貌之间的关系。结果表明，通过在复合膜活性层中引入强亲水性的磺酸基和全刚性主链的Cardo型聚醚砜，复合膜在保持较高盐截留率(97.3%)情况下，水通量得到了大幅度的提高，达到了51.2 L/m2.h。 4．合成了新型的全刚性芳香主链的两性聚电解质SPES-NH3+，并对其溶液性质和自组装行为进行了详细的研究。结果表明，在一定的溶液pH值下，两性聚电解质SPES-NH3+表现出聚阴离子的性质。另外，通过引入[BMIM]+离子屏蔽磺酸根负离子，我们在没有加入其它聚电解质的情况下，成功地制备了[BMIM]SPES-NH3+多层膜，并对多层膜表面性质进行了研究。结果表明，多层膜的厚度可由层数来控制，并且膜表面较平滑，其RMS值为6 nm。这种新的组装方式为构筑刚性主链的两性聚电解质多层膜提供了新的方法。

热可交联聚酰亚胺/高性能热塑性树脂共混体系的研究

1．热可交联聚酰亚胺／高性能热塑性树脂共混体系的研究聚苯硫醚［Poly（phenylene sulfide），PPS］是由刚性结构的苯环和柔性的硫醚连接起来，交替排列构成的线性高分子化合物，具有高的热稳定性、良好的耐化学药品性、优良的电绝缘性、耐老化性和阻燃性等综合性能优异的高性能树脂。聚醚矾〔Poly（ether sulfone），PES］是一种非结晶性的热塑性工程塑料一，具有优异的热稳定性、耐高温蠕变性及优异的物理机械性能。其高的玻璃化转变温度（Tg=225℃），使其可以在较高温度下作为结构材料使用。本论文研究了PPS/PES二元共混物的热性能和动态力学性能，并以热可控交联的低分子量多官能单体PMR-POI（聚醚酰亚胺）为界面增强剂，分别研究了POI与PPS、PES之间的接枝和／或交联反应，POI对PPS结晶行为的影响，POI对PES分子运动的影响和POI对PPS/PES共混体系的界面增强。主要结果如下：1．PPS/PES共混物相容性的特征在于选择性的部分相容，少量的非晶PPS分子可以扩散进入PES相区，相反的扩散过程则不会发生。2．PPS/PES共混物的热学性质和动态力学性能主要受连续相的控制。3．PPS相的性能主要受其结晶度的影响，因此能够改变其结晶度的因素均会改变PPS相的性质。4．光谱学和流变的证据表明，POI同PES，PPs共混过程中有接枝反应发生，分子链增长，分子量加大。这种接枝和／或交联反应的程度是热可控的。5．POI是PPS的增塑剂，成核剂和扩链剂，与POI共混使得PPS结晶速率增加，平衡熔点上升，表面折叠自由能降低。6；在PES/POI体系中Pol对PEs起到了增塑的作用，Tg降低，经高温热处理后Tg上升。因此，POI对PES性能的影响也是热可控的。7．PMR-POI能够在PPS/PES共混体系中有效地扩散并起到了降低分散相粒子的尺寸、增强界面的作用。它是该共混体系的有效界面增强剂。8．"高温退火既能够提高扩散速率也能够提高反应速率；二者相互竞争。2．马来酸配封端溉碳酸丙撑酯的研究二氧化碳与环氧丙烷交替共聚物（polypropylene careonate，PPC）是由二氧化碳活化并与环氧丙烷共聚而成的一类可完全生物降解的新型高分子材料，具有巨大的潜在应用价值。本论文讨论了马来酸配封端的聚碳酸丙撑酯（MA-PPC）和未封端的PPC的粘弹性、流变行为以及热降解和热分解行为，并得出如下结论：1．马来酸配封端抑制了PPC解拉链式的热分解和无规链断裂热降解，PPC的热稳定性和力学性能得到提高。2．PPC和MA-PPC在玻璃化转变温度有相似的自由体积分数，PPC的Tg比MA-PPC稍低。虽然PPC和MA-PPC玻璃化转变表观活化能E。和平均松弛时间T随温度升高单调降低，但PPC的分子运动对温度更敏感，而MA-PPC较稳定。马来酸配封端改变了PPC分子运动的特征及松弛行为，许多实验证据证明，这是由于封端后的PPC大分子链间的相互作用增强及分子链缠结密度增加。3．MA-PPC在70℃左右会发生脱水，实现大分子偶联反应并得到变温红外光谱、分子量成倍增加及线膨胀数据的有力支持。4．用零剪切粘度几。的方法测得PPC及MA－PPC加工过程中的热降解温度，它们分别为150℃和175℃，在此温度以上，η0降低速率的增加归因于大分子的主链断裂以及解拉链反应。5．测得了PPC的临界缠结分子量，它几乎是MA-PPC相应值（6613）的3倍。这表明马来酸配封端不仅改善了PPC的熔体弹性，而且也大大增强了PPC的缠结密度以及分子链间的相互作用。6．在本实验条件下在氮气和空气的气氛中，MA-PPC同PPC的热降解和热分解行为几乎一致，即在PPc的加土过程可以忽略氧气对其的影响。7．虽然MA-PPC的玻璃化温度在40℃左右，但在40℃-120℃的温度区间内，MA-PPC达不到粘流状态。8．没有剪切力时在120℃-150℃，30分钟内，MA-PPC几乎没有降解，在静态条件下，低于170℃时，MA-PPC的解拉链式降解是十分轻微的，当温度超过170℃，PPC降解相当严重。9．在热机械力存在的情况下，发生无规断链的机会增加，无规断链又会加速解拉链降解，因此实际加工中的加工窗口比静态下窄，MIA-PPC的加工窗口应为130℃-160℃。10．MA-PPC的热分解过程是一步完成的，热分解温度随升温速率的加快而提高，并计算出热分解的表观活化能为623.3KJ／mol。

Synthesis and characterization of novel sulfonated polyimides from 1,4-bis(4-aminophenoxy)-naphthyl-2,7-disulfonic acid

A novel sulfonated diamine monomer, 1,4-bis(4-aminophenoxy)-naphthyl-2,7-disulfonic acid (BAPNDS), was synthesized. A series of sulfonated polyimide copolymers were prepared from BAPNDS, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) and nonsulfonated diamine 4,4'-diaminodiphenyl ether (ODA). Flexible, transparent, and mechanically strong membranes were obtained. The membranes displayed slightly anisotropic membrane swelling. The dimensional change in thickness direction was larger than that in planar. The novel SPI membranes showed higher conductivity, which was comparable or even higher than Nafion 117. Membranes exhibited methanol permeability from 0.24 x 10(-6) to 0.80 X 10(-6) cm(2)/s at room temperature, which was much lower than that of Nafion (2 x 10-6 CM2/s). The copolymers were thermally stable up to 340 degrees C. These preliminary results have proved its potential availability as proton-exchange membrane for PEMFCs or DMFCs.

Thermal and dynamic mechanical properties of PES/PPS blends

Blends of poly(ether-sulfone) (PES) and poly(phenylene sulfide) (PPS) with various compositions were prepared using an internal mixer at 290degreesC and 50 rpm for 10 min. The thermal and dynamic mechanical properties of PES/PPS blends have been investigated by means of DSC and DMA. The blends showed two glass transition temperatures corresponding to PPS-rich and PES-rich phases. Both of them decreased obviously for the blends with PES matrix. On the other hand, T-g of PPS and PES phase decreased a little when PPS is the continuous phase. In the blends quenched from molten state the cold crystallization temperature of PPS was detected in the blends of PES/PPS with mass ratio 50/50 and 60/40. The melting point, crystallization temperature and the crystallinity of blended PPS were nearly unaffected when the mass ratio of PES was less than 60%, however, when the amount of PES is over 60% in the blends, the crystallization of PPS chains was hindered. The thermal and the dynamic mechanical properties of the PPS/PES blends were mainly controlled by the continued phase.

Syntheses and properties of novel polyimides derived from 2-(4-aminophenyl)-5-aminopyrimidine

2-(4-Aminophenyl)-5-aminopyrimidine (4) is synthesized via a condensation reaction of vinamidium salts and amidine chloride salts, followed by hydrazine palladium catalyzed reduction. A series of novel homo- and copolyimides containing pyrimidine unit are prepared from the diamine and 1,4-phenylenediamine (PDA) with pyromellitic dianhydride (PMDA) or 3,3',4,4'-biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two-step thermal imidization method. The poly(amic acid) precursors had inherent viscosities of 0.97-4.38 dL/g (c = 0.5 g/dL, in DMAc, 30 degrees C) and all of them could be cast and thermally converted into flexible and tough polyimide films. All of the polyimides showed excellent thermal stability and mechanical properties. The glass transition temperatures of the resulting polyimides are in the range of 307-434 degrees C and the 10% weight loss temperature is in the range of 556-609 degrees C under air. The polyimide films possess strength at break in the range of 185-271 MPa, elongations at break in the range of 6.8-51%, and tensile modulus in the range of 3.5-6.46 GPa. The polymer films are insoluble in common organic solvents, exhibiting high chemical resistance.

Syntheses of biphenyl polyimides via nickel-catalyzed coupling polymerization of bis(chlorophthalimide)s

A facile method for the synthesis of biphenyl polyimides, which involves the nickel-catalyzed coupling of aromatic dichlorides containing imide structure in the presence of zinc and triphenylphosphine, has been developed. The polymerizations proceeded smoothly under mild conditions and produced biphenyl polyimides with inherent viscosities of 0.13-0.98 dL/g. The polymerizations of bis(4-chlorophthalimide)s with bulky side substituents gave high molecular weight polymers. Low molecular weight polymers from bis(4-chlorophthalimide)s containing rigid diamine moieties and bis(3-chlorophthalimide)s were obtained because of the formations of polymer precipitate and cyclic oligoimides, respectively. The effects of various factors, such as amount of catalyst, solvent volume, ligand, reaction temperature, and time, on the polymerization were studied. The random copolymerization of two bis(chlorophthalimide)s in varying proportions produced medium molecular weight material. The TgS of prepared polyimides were observed at 245-311 degreesC, and the thermogravimetry of polymers showed 10% weight loss in nitrogen at 470-530 degreesC.