【作者】 王建宇；

【导师】 徐又一；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2008， 博士

【摘要】 PVC、PVDF及PSF是最常用的微滤、超滤膜材料,但在实际应用中,面临通量小、易污染、选择性和功能单一等问题,因此,对其进行亲水化和功能化改性以提高综合性能,具有重要意义。近年,研究发现,将两亲性共聚物与膜材料共混并通过相转化法制膜,则两亲性共聚物发生表面迁移而富集在共混膜的表面,亲水链段的表面富集使共混膜的亲水性得以改善,而疏水链段可与膜材料分子链发生链缠结、对亲水链段起到“锚定”的作用,使亲水改性效果持久、稳定。其中,两亲性共聚物的疏水链段与膜材料的相容性对共混膜性能有着重要影响,因而两亲性共聚物的分子设计与合成是关键、也是难点。在本研究中,设计并合成了多种不同化学组成和分子结构的两亲性共聚物,然后将之与PVC、PVDF及PSF共混制备了多孔膜,考察了两亲性共聚物对共混膜结构及性能的影响。具体研究内容和主要结论概述如下:通过ATRP法合成了PVC-g-P（PEGMA）。该共聚物在水中溶胀而不溶解,数均分子量为5.5×10⁵g/mol,P（PEGMA）链段含量为82.6wt%。将PVC-g-P（PEGMA）与PVC共混并通过浸没沉淀法制备了PVC-g-P（PEGMA）/PVC多孔膜,研究发现:PVC-g-P（PEGMA）主要分布在共混膜的表面,当两亲性共聚物添加量为15wt%时,共混膜表面P（PEGMA）的摩尔百分数达到43%;两亲性共聚物的引入,提高了共混膜的孔隙率和平均孔径;其初始纯水接触角为52.2°,15s后下降到0°;0.1MPa、25℃下共混膜的纯水通量为584.4 L/m²·h,对BSA的截留率大于92%,水通量恢复率为84.7%。通过RAFT法合成了具有“梳子-链段-梳子”结构的ABA型两亲性共聚物P（PEGMA）-PMMA-P（PEGMA）,其数均分子量为1.9×10⁴g/mol。以PVDF为大分子引发剂,通过ATRP法合成了两亲性共聚物PVDF-g-PMAG,其数均分子量为3.12×10⁵g/mol,PMAG含量为65.7wt%。分别将P（PEGMA）-PMMA-P（PEGMA）和PVDF-g-PMAG与PVDF共混并制备多孔膜。研究发现,两亲性共聚物的引入,增加了膜的孔隙率;引入少量的共聚物之后（～5wt%）,PVDF膜的纯水接触角从110°降至50～56°,降幅超过50%;此外,共混膜的抗蛋白质吸附能力也得到了显著的提高。以PSF-CH₂Cl为大分子引发剂,通过ATRP法合成了PSF-g-P（PEGMA）,其数均分子量为6.34×10⁴g/mol,P（PEGMA）的摩尔百分含量为71.1%,质量百分含量为39.6 wt%。该共聚物在水中溶胀而不溶解,将它与PSF共混并制备PSF-g-P（PEGMA）/PSF共混膜。研究结果显示,PSF-g-P（PEGMA）的引入,改善了共混膜的孔结构、提高了孔隙率和平均孔径;PSF-g-P（PEGMA）主要分布在共混膜的表面;将共混膜置于90℃热水中浸泡24h进行热处理后,膜表面富集的PSF-g-P（PEGMA）量明显增加;对于PSF-g-P（PEGMA）含量为20wt%的共混膜,初始纯水接触角为43.5°,50s后下降到0°;对BSA吸附量接近0。以Br-PSF-Br为引发剂,通过ATRP法合成了以PSF为疏水链段（B段）、分别以P（PEGMA）和PMAG为亲水链段（A段）的ABA型两亲性共聚物;P（PEGMA）-PSF-P（PEGMA）和PMAG-PSF-PMAG,所合成的共聚物在水中溶胀而不溶解。将这两种共聚物分别与PSF共混制备共混膜,研究发现,由于两亲性共聚物的引入,PSF膜表面由致密、无孔变为多孔（孔径小于50 nm且分布均匀）,且膜皮层变薄、指状孔亚层结构变得更加规整、均一,整个膜的孔隙率变大:随着共混膜中两亲性共聚物含量的增加,其水接触角和BSA吸附量逐渐下降,当共聚物添加量为10 wt%时,BSA的吸附量接近于0。通过ATRP法合成了PSF-g-PtBA和PSF-g-PNIPAAm,然后在酸性条件下对PSF-g-PtBA进行水解,得到PSF-g-PAA。PSF-g-PAA和PSF-g-PNIPAAm的数均分子量分别为5.04×10⁴g/mol和5.58×10⁴g/mol。将PSF-g-PAA或（和）PSF-g-PNIPAAm与PSF共混,通过浸没沉淀法制备了20wt%PSF-g-PAA/PSF（A）、20wt%PSF-g-PNIPAAm/PSF（B）及10wt%PSF-g-PAA/10wt%PSF-g-PNIPAAm/PSF（C）三种共混膜。研究发现,引入共聚物后,共混膜的孔隙率和平均孔径有所提高;两亲性共聚物主要分布在共混膜的表面;A、B、C三种共混膜可分别在35s、90s及120s内被H₂O完全浸润:不同pH值和温度下的水通量测量发现,A膜具有pH响应性,B膜具有温度响应性,C膜则具有pH/温度双重响应功能。更多还原

【Abstract】 PVC,PVDF,and PSF have been widely used to fabricate polymeric Microfiltration and Ultrafiltration membranes for decades.However,their hydrophobic character makes them highly susceptible to fouling.A second problem limiting the applications of PVC,PVDF,and PSF membranes is their poor flux,selectivity,and functions.An obvious approach to solving the problems of fouling and selectivity is the surface modification of these hydrophobic membranes to impart engineered surface chemistries.Compared to the conventional surface modification methods such as coating and grafting,blending is a facile and efficient method to prepared hydrophilic membranes.Over the past decades,many studies have been devoted toward the development of methods to modify the surfaces of polymeric membranes through the surface segregation of amphiphilic polymer additives.When an amphiphilic copolymer is blended with the hydrophobic membrane materials and prepared a blend membrane via immersion-precipitation process,the amphiphilic copolymer can preferentially segregated to the surfaces of blend membranes,and the location of amphiphilic copolymer at membrane surface results in the formation of a hydrophilic "brush" of the hydrophilic chains,while the hydrophobic segments intermixes with the membrane base component,serving as an anchor for the additives.In this method, the performances of blend membranes are depend to a large extent on the compatibility between the membrane base component and the hydrophobic segments of the amphiphilic copolymers,thus,the molecular design and synthesis of the amphiphilic copolymer additives is very important.With this in mind,in this thesis, we designed and synthesized a series of amphiphilic copolymers with various chemical composition and molecular structures,the using those copolymers as additives to prepared hydrophilic and anti-fouling PVC,PVDF,and PSF blend membranes were also studied.An amphiphilic graft copolymer which having PVC as the hydrophobic chains and P（PEGMA） as the hydrophilic chains,i.e.PVC-g-P（PEGMA）,have been synthesized via ATRP.The molecular weight of PVC-g-P（PEGMA） which calculated based on ¹H-NMR was 5.5×10⁵ g/mol,the weight fraction of P（PEGMA） was 82.6wt%.PVC-g-P（PEGMA） was used as an additives to modified PVC membranes, the investigation results demonstrated that PVC-g-P（PEGMA） were mainly located on the membrane surfaces and impart the blend membranes with excellent hydrophilicity and anti-fouling properties.For instance,when the weight fraction of PVC-g-P（PEGMA） in blend membrane was 15wt%,the initial water contact angle of the blend membrane was 52.2°,and the water contact angle decreased to 0°within 15s, the pure water flux of 15wt%PVC-g-P（PEGMA）/PVC membrane was 584.4 L/m²·h, the BSA rejection ratio was higher than 92%,the water flux recovery was 84.7%.An ABA type amphiphilic copolymer with "comb-block-comb" structure,i.e. P（PEGMA）-PMMA-P（PEGMA）,was synthesized via two steps RAFT.On the other hand,a amphiphilic graft copolymer which containing PVDF as hydrophobic backbone and having an sugar-carrying polymer as the hydrophilic side chains,i.e. PVDF-g-PMAG,was synthesized via ATRP using PVDF as macroinitiator.The GPC molecular weights of P（PEGMA）-PMMA-P（PEGMA） and PVDF-g-PMAG was 1.9×104 g/mol and 3.12×105 g/mol,respectively.When small amounts（less than 5wt%） of P（PEGMA）-PMMA-P（PEGMA） or PVDF-g-PMAG was blend with PVDF to prepare PVDF blend membranes,the water contact angle of PVDF membranes decreased from 110°to 50～56°.Beside this,the protein-resistance properties of PVDF blend membranes were also enhanced greatly.Using PSF-CH₂Cl as macroinitiator,an amphiphilic copolymer which having PSF as the hydrophobic backbone and with P（PEGMA） as the hydrophilic side chains, i.e.PSF-g-P（PEGMA）,was synthesized via ATRP.The molecular weight of PSF-g-P（PEGMA） was calculated as 6.34×10⁴ g/mol based on IH-NMR results,the molar fraction and weight fraction of P（PEGMA） in the copolymer was 71.1%and 39.6 wt%,respectively.PSF-g-P（PEGMA） can be swollen but were not soluble in H20.A series of blend membranes containing various amounts of PSF-g-P（PEGMA） were prepared via phase inversion process.The investigation results showed that the introduction of PSF-g-P（PEGMA） can obviously improved the hydrophilicity and anti-fouling property of PSF blend.For example,the initial water contact angle of 20wt%PSF-g-P（PEGMA）/PSF membrane was 43.5°,after 50s,the blend membrane was completely wetted by water.The apparent BSA adsorption amount of the 20wt%PSF-g-P（PEGMA）/PSF membrane was extreme low compared to that of the pure PSF membrane.Two kind of ABA type amphiphilic copolymer having PSF segment as the hydrophobic composition,i.e.P（PEGMA）-PSF-P（PEGMA） and PMAG-PSF-PMAG, respectively,were synthesized via ATRP,using a difunctional PSF as macroinitiator. The molecular weights and molecular weights distributions of these copolymers were determined by GPC.P（PEGMA）-PSF-P（PEGMA） and PMAG-PSF-PMAG were not soluble in water but they can be swollen by water.The porous membranes prepared from the blends of P（PEGMA）-PSF-P（PEGMA） or PMAG-PSF-PMAG with PSF exhibited higher porosity and average pore diameters.Moreover,when the contents of the amphiphilic copolymer in the blend membranes was 10wt%,the apparent BSA adsorption of blend membrane were neared to zero.PSF-g-PtBA and PSF-g-PNIPAAm were synthesized by ATRP,using PSF-CHECI as macroinitiator.After acidolysis treatment,the tert-butyl groups on PSF-g-PtBA were completely removed,thus an amphiphilic copolymer,i.e.PSF-g-PAA,was obtained.The molecular weights of them were determined by GPC（5.04×10⁴ g/mol for PSF-g-PAA and 5.58×10⁴ g/mol for PSF-g-PNIPAAm,respectively）.Three kinds of blend membranes were prepared from the blends of PSF-g-PAA or/and PSF-g-PNIPAAm,i.e.20wt%PSF-g-PAA/PSF（A）,20wt%PSF-g-PNIPAAm/PSF（B）, and 10wt%PSF-g-PAA/10 wt%PSF-g-PNIPAAm/PSF（C）,respectively.Water contact angle measurement result demonstrated that A,B,and C membrane can be wetted by water within 35s,90s,and 120s,respectively.Moreover,the water flux of A was pH-dependent,the water flux of B was temperature-dependent,and the water flux of C was pH and temperature dual- dependent.更多还原