Thermal and Morphological Studies on Poly(Methyl Methacrylate)/Thermoplastic Polyurethane Blends

Poly(methyl methacrylate) (PMMA) and thermoplastic polyurethane (TPU) blends in different compositions viz., 95/05, 90/10, 85/15 and 80/20 (by wt/wt% of PMMA/TPU) have been prepared by melt mixing using a twin screw extruder. The thermal stability of these blends has been characterized by thermogravimetric (TG) analysis. All the blends are stable up to 381°C and complete degradation occurs at 488°C. A slight improvement in thermal stability was noticed with an increase in TPU content in the blends. Surface morphology of the blends has been studied by an optical microscope. Optical microphotographs revealed two‐phase morphology for all the blends.     

Additive Effects of Lithium Salts with Various Anionic Species in Poly (Methyl Methacrylate)

We report that lithium salts in lithium-ion batteries effectively modify the physical properties of poly (methyl methacrylate) (PMMA). The glass transition temperature (T_g) is an indicator of the heat resistance of amorphous polymers. The anionic species of the salts strongly affected the glass transition behavior of PMMA. We focused on the additive effects of various lithium salts, such as LiCF₃SO₃, LiCOOCF₃, LiClO₄, and LiBr, on the T_g of PMMA. The large anions of the former three salts caused them to form macroscopic aggregates that acted as fillers in the PMMA matrix and to combine the PMMA domains, increasing T_g. On the other hand, LiBr salts dispersed microscopically in the PMMA matrix at the molecular scale, leading to the linking of the PMMA chains. Thus, the addition of LiBr to PMMA increased T_g as well as the relaxation time in the range of glass to rubber transition.     

脂肪族聚碳酸酯型聚氨酯/聚甲基丙烯酸甲酯互穿网络聚合物的研究

用同步法合成了聚碳酸亚丙酯聚氨酶／聚甲基丙烯酸甲醇互穿网络聚合物（PPCPU／PMMA，IPN），调节IPN中两组分配比制备出多种高聚物共混物。用DSC、TEM对IPN的研究结果表明．PPCPU／PMMA之IPN的两组分是互不相容的。同时对各种组成比的IPN材料进行力学性能测试，并用SEM对断面进行了观察，发现IPN的密度大于相应体系体积加和值。     

聚甲基丙烯酸甲酯与聚醋酸乙烯酯共混的红外光谱研究

用红外光谱(FTIR)研究了聚甲基丙烯酸甲酯(PMMA)与聚醋酸乙烯酯(PVAc)共混体系相容性,在160℃以上共混体系发生相分离;分相体系与非分相体系的FTIR谱明显不同;共混体系的FTIR谱不能从两统组分红外光谱简单加和得到;结果表明大分子构象发生了变化,PMMA/PVAc体系相容可能是大分子构象熵变所致。     

Poly(Methyl Methacrylate) Coatings Containing Flame Retardant Additives from Suspensions in Water-2-Propanol

A dip-coating technique is designed for deposition of poly(methyl methacrylate) (PMMA) from water/2-propanol mixture, avoiding the use of traditional toxic solvents. Solutions of PMMA macromolecules with high molecular weight (M_W) are obtained for a water/2-propanol ratio of 0.15–0.33 and the solubilization mechanism is discussed. The ability to use concentrated PMMA solutions and high M_W of the polymer are the key factors for the successful dip coating deposition. The coating mass for 10 g L⁻¹ polymer solutions shows a maximum at a water/2-propanol ratio of 0.25. The deposition yield increases with the polymer concentration increase and with an increasing number of the deposited layers. PMMA deposits protect stainless steel from aqueous corrosion. The coating technique allows for the fabrication of composite coatings, containing flame-retardant materials (FRMs), such as commercial halloysite, huntite, hydrotalcite, and synthesized Al(OH)₃, in the PMMA matrix. The FRM content in the coatings is modified by variation of the FRM content in colloidal suspensions. A fundamentally new method is developed, which is based on the salting out aided dispersive extraction of Al(OH)₃ from the aqueous synthesis medium to 2-propanol. It is based on the use of hexadecylphosphonic acid molecules as extractors. The method offers advantages of reduced agglomeration.     

PMMA/PC Blends: Effect of Mixing Conditions on Compatibility

In this work the effect of melt mixing condition and of a trans-esterification catalyst on miscibility of poly(methyl methacrylate) (PMMA)/polycarbonate of bisphenol A (PC) blends is studied. In particular, at high temperature chemical reactions between PMMA and PC phases can take place; these strongly change the compatibility in the blend and materials having single T_g can be obtained. FT-IR analyses, coupled with solvent extraction, suggest that a grafting reaction of PC on PMMA is involved. SEC and DSC data are consistent with spectroscopic results, and some decrement of the molar weight distribution (MWD) of PC phase is observed. On the other hand, the presence of a fraction of modified material having higher MWD of starting PMMA is also noticed. The single T_g characteristic of some materials has been confirmed by experimental data of structural relaxation performed by differential scanning calorimetry (DSC). These materials showed optical clarity and the morphological analysis performed by scanning electron microscopy (SEM) confirm the homogeneity of these materials.     

Preparation of Latexes with Poly(Methyl Methacrylate) Cores and Hydrophilic Polymer Shells Containing Amino Groups

Abstract

Functional latexes with poly(methyl methacrylate) (PMMA) cores and amino‐containing, water‐soluble polymer shells were synthesized via direct graft copolymerization of methyl methacrylate from water‐soluble polymers induced by a small amount of tert‐butyl hydroperoxide (TBHP) at 80°C for 2 h. Amphiphilic graft copolymers and PMMA homopolymers were generated concurrently to form highly monodispersed latexes. The effects of water‐soluble polymer containing different amino group, reaction temperature, TBHP concentration, molecular weight of the polymer and pH of the solution on conversion and grafting efficiency of the monomer and particle size were investigated. Transmission electron microscopic images of the PMMA/poly(ethyleneimine) (PEI) and PMMA/poly(allylamine) (PAA) particles clearly show well‐defined core‐shell morphologies, where PMMA cores are coated with either PEI or PAA shell. The amino‐containing polymer shells were also confirmed with zeta‐potential measurements. Furthermore, the amino‐containing latexes can be produced with a solids content up to 22 wt.%. Thus, this method provides a commercially viable route to functional latexes.     

Atom Transfer Radical Polymerization of Methyl Methacrylate Using Telechelic Tribromo Terminated Polyurethane Macroinitiator

Novel telechelic tribromo terminated polyurethane (Br₃-PU-Br₃) was used as a macroinitiator in atom transfer radical polymerization (ATRP) of methyl methacrylate using CuBr as a catalyst and NN,N',N”,N”-pentamethyldiethylenetriamine (PMDETA) as a ligand. During the course of polymerization, poly(methyl methacrylate)-b-polyurethane-b-poly(methyl methacrylate) (PMMA-b-PU-b-PMMA) tri-block copolymers were formed. The resulting tri-block copolymers were characterized by gel permeation chromatography (GPC) and ¹H nuclear magnetic resonance (NMR) spectroscopy. Molecular weight of the tri-block copolymers increases with increasing conversion. This result shows Br₃-PU-Br₃/CuBr/PMDETA initiating system polymerized methyl methacrylate through ATRP mechanism. NMR spectroscopy results revealed that apart from bromine atom transfer from Br₃-PU-Br₃ to PMDETA-CuBr complex, bromine atom transfer from the initially formed tri-block copolymer to PMDETA-CuBr complex also takes place, and, as a result, double bond terminated copolymer formed. Mole ratio of polyurethane and poly(methyl methacrylate) present in the PMMA-b-PU-b-PMMA tri-block copolymers was calculated using ¹H-NMR spectroscopy and it was found to be comparable with the mole ratio calculated through GPC results. Differential scanning calorimetric results confirmed the presence of two different phases in the tri-block copolymers.     

Gelation Dynamics and Mechanism(s) in Stereoregular Poly(Methyl Methacrylate)s

Chain conformation and gel structure of syndiotactic PMMA thermoreversible gels have been investigated using small angle neutron scattering (SANS). A double helix model for the chain conformation is proposed alongside a gel network model where the fibrils are formed by the proposed double helix and the junctions by the aggregation of 3 double helices. Preliminary results, also obtained by SANS, for stereocomplex gels prepared in bromobenzene are presented.     

Thermal crosslinking of poly(methyl methacrylate) by reaction of methyl ester and quaternary ammonium salt and application to (meth)acrylate-based TPEs

Copolymers of N-vinylbenzyl N-methyl pyrrolidinium chloride (VBMPC) and methyl methacrylate, PVBMPC-co-poly(methyl methacrylate) (PMMA), were synthesized by free-radical copolymerization and proved to be prone to crosslinking as a result of the reaction of methyl ester groups with benzyl methyl pyrrolidinium chloride (BMPC) moieties at temperatures higher than 110 °C. When the VBMPC content was lower than 20 wt %, these copolymers were miscible with homo-PMMA. Blends of homo-PMMA and PVBMPC-co-PMMA fully could be cured above 150 °C, when the molecular weight of PMMA exceeded 10,000 and the VBMPC content of the copolymer was higher than 5 wt %. This reaction was carried out to crosslink selectively the PMMA microdomains of PMMA-b-poly(isooctyl acrylate) (PIOA)-b-PMMA (MIM) triblock copolymers to explain the mechanism for the mechanical failure of fully (meth)acrylic thermoplastic elastomers. Comparison of the ultimate tensile properties of MIM block copolymers, when the dispersed PMMA phases and PIOA matrix were crosslinked, led to the conclusion that the ductile failure of the hard PMMA microdomains rather than the elastic failure of the PIOA matrix was the reason for the mechanical failure of MIM triblocks. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4402–4411, 1999     

Characterisation of Hyaluronic Acid Blends Modified by Poly(N-Vinylpyrrolidone)

The viscosity behaviour and physical properties of blends containing hyaluronic acid (HA) and poly(N-vinylpyrrolidone) (PVP) were studied by the viscometric technique, steady shear tests, tensile tests and infrared spectroscopy. Viscometric and rheological measurements were carried out using blends of HA/PVP with different HA weight fractions (0, 0.2, 0.5, 0.8 and 1). The polymer films and HA/PVP blend films were prepared using the solution casting method. The study of HA blends by viscometry showed that HA/PVP was miscible with the exception of the blend with high HA content. HA and its blends showed a shear-thinning flow behaviour. The non-Newtonian indices (n) of HA/PVP blends were calculated by the Ostwald–de Waele equation, indicating a shear-thinning effect in which pseudoplasticity increased with increasing HA contents. Mechanical properties, such as tensile strength and elongation at the break, were higher for HA/PVP films with w_HA = 0.5 compared to those with higher HA contents. The elongation at the break of HA/PVP blend films displayed a pronounced increase compared to HA films. Moreover, infrared analysis confirmed the existence of interactions between HA and PVP. The blending of HA with PVP generated films with elasticity and better properties than homopolymer films.     

Effect of Some Solvents on the Radical Polymerization of Methyl Methacrylate Studied by Differential Scanning Calorimetry

The course of the isothermal polymerization of methyl methacrylate in different concentrated solutions in toluene, n-butyl acetate, cyclohexanone, and dimethylformamide was measured at four temperatures by differential scanning calorimetry. The conversions at the sharp increase of the reaction rate were found to increase with dilution of the reaction mixture. The polymerization enthalpies and the composite rate constants were calculated. The polymerization enthalpies seem to be solvent independent. The composite rate constants for polymerization in butyl acetate are lower and those for polymerization in toluene are equal to the constants for bulk polymerization. They are independent of the concentration of the reaction system. The constants for polymerization in cyclohexanone and dimethylformamide are, however, concentration dependent. An interrelation between the composite rate constants and solubility parameters of the solvents and methyl methacrylate was found. The relative molecular weight averages decrease with decreasing concentration of the reaction mixture. The MW distributions were very broad.     

聚环氧乙烷／脂肪族聚碳酸酯共混研究

本文用差热分析(DSC)和红外光谱仪(FTIR)研究了聚环氧乙烷(PEO)和新型聚合物——脂肪族聚碳酸脂(PPC)共混热行为和大分子间的相互作用。由熔点下降方法给出PEO/PPC混合体系在320K下相互作用参数为-0.46;FTIR谱表明PPC大分子链和PEO大分子链存在较强的相互作用;PEO/PPC共混形态随PPC含量增加发生了较大变化。     

聚甲基丙烯酸甲酯/聚(苯乙烯-丙烯腈)共混体系相分离的特征动态流变响应

采用动态流变学方法,结合小角激光光散射(SALLS)测定,对聚甲基丙烯酸甲酯(PMMA)/聚(苯乙烯－丙烯腈)(SAN)共混体系的动态流变行为与相分离的关系进行了研究.发现在低频区域,时温叠加失效与共混物体系发生相分离有关,时温叠加失效温度T_b与用SALLS测定的浊点温度T_c一致,用低频区域动态储能模量G'与频率的关系[1gG'～lg(α_T)]偏离线性粘弹模型或时温叠加失效温度表征PMMA/SAN共混体系的相分离是有效的.     

聚甲基丙烯酸甲酯与苯乙烯-丙烯腈共聚物混合体系相分离初期的固体NMR研究

本文用氢谱宽线固体NMR技术研究了聚甲基丙烯酸甲酯(PMMA)和苯乙烯-丙烯腈共聚物(SAN)混合体系不稳相分离初期阶段, 得到了在分相过程中弛豫谱的变化规律, 测定了相分离增长速率。结果指出: 随着退火时间的增加, 两相体系形成; 大分子扩散方式是由浓度低的区域向浓度高的区域扩散, 扩散系数为负值; 相分离增长速率的数量级与用光散射研究的结果相同; 分子相互作用的相关距离为46.5 nm。     

聚环氧氯丙烷聚氨酯／聚甲基丙烯酸甲酯IPN力学性能

利用改变组成比、聚氨酯ＰＵ软段的分子量、Ｒ值、异氰酸酯和两网络各自交联剂含量合成出５个系列的聚环氧丙烷聚氨酯／聚甲基丙烯酸甲酯互穿聚合物网络，利用ＩＰＮ中交联、互穿、缠结程度的不同，并结合ＤＣＳ、ＴＥＭ、动态粘弹谱讨论了ＩＰＮ力学性能。