Synthesis of a star‐shaped poly(ethylene‐co‐propylene) copolymer as a viscosity index improver for lubricants

A saturated star‐shaped poly(ethylene‐co‐propylene) copolymer, (EP)_star, has been synthesized for use as a viscosity index improver in lubricants. Polyisoprene arms were first anionically synthesized using n‐butyllithium as the initiator, followed by a linking reaction with divinylbenzene at the optimum temperature of 60°C. The resulting star‐shaped polyisoprene, (I)_star, was then hydrogenated to eliminate the double bonds of the polyisoprene forming the poly(ethylene‐co‐propylene) structure. The degree of branching (number of arms on each molecule) increases with increase in the mole ratio of divinylbenzene to n‐butyllithium. Increasing the arm length adversely affects the linking efficiency and a minimum amount of tetrahydrofuran (THF) at a THF:n‐butyllithium molar ratio of 1.12 was needed in order to achieve a maximum linking efficiency of approximately 85%. The T_g of poly(ethylene‐co‐propylene) is about 10°C higher than that of the original polyisoprene. Compared with (I)_star, (EP)_star has a thermal decomposition temperature that is 50°C higher but is independent of the arm length or the degree of branching. Viscosity measurement results for (EP)_star reveal that intrinsic viscosity depends only on the arm length but not the degree of branching. Adding 1 wt % of (EP)_star markedly increases the viscosity index of a LN base oil. The addition of 1 wt % of (EP)_star increases the viscosity index (95 for base oil) up to a number between 111 and 145, with the exact number depending upon its arm length and degree of branching. With a fixed arm length, an (EP)_star having a higher degree of branching increases the viscosity index more than one having a lower degree of branching. On the other hand, the viscosity index increases with increase in the arm length when the degree of branching is fixed. Adding 1 wt % of (EP)_star also causes a change in the pour point of the lubricant with the pour point decreasing with increase in the degree of branching. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1911–1918, 2002     

Synthesis of polystyrene‐b‐poly(ethylene‐co‐butene) block copolymers by anionic living polymerization and subsequent noncatalytic hydrogenation

A series of polystyrene‐b‐polybutadiene (PSt‐b‐PBd) block copolymers with various chain lengths and compositions were synthesized by sequential living anionic polymerization and then converted into the corresponding polystyrene‐b‐poly(ethylene‐co‐butene) (PSt‐b‐PEB) block copolymers through the selective hydrogenation of unsaturated polybutadiene segments. Noncatalytic hydrogenation was carried out with diimide as the hydrogen source. The microstructures of PSt‐b‐PBd and PSt‐b‐PEB were investigated with gel permeation chromatography, ¹H‐NMR, ¹³C‐NMR, Fourier transform infrared, and differential scanning calorimetry. The results showed that the hydrogenation reaction was conducted successfully and that the chain length and molecular weight distribution were not altered by hydrogenation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2632–2638, 2006     

润滑油粘度指数改进剂的使用性能与发展

介绍了粘度指数改进剂（VII）的作用原理和使用性能要求，概述了国内外研究和生产的几种粘度指数改进剂，对聚甲基丙烯酸酯（PMA）、乙丙共聚物（OCP）、氢化苯乙烯双烯共聚物（HSD）等几种粘度指数改进剂在国内外的发展情况进行了综述。     

Enhancement of the high‐temperature utility of a polystyrene‐b‐poly(ethylene‐co‐butylene)‐b‐polystyrene block copolymer by friedel–crafts naphthoylation

A procedure was developed for the Friedel–Crafts naphthoylation of the polystyrene segments of a polystyrene‐b‐poly(ethylene‐co‐butene)‐b‐polystyrene (SEBS) triblock copolymer. It was possible to obtain up to 72% 1‐naphthoylation or 100% 2‐naphthoylation of the polystyrene segments in the copolymer. Naphthoylation could also be accomplished using trifluoromethanesulfonic acid as a catalyst. The naphthoylated products were characterized by ¹H‐NMR spectroscopy, size‐exclusion chromatography, and dynamic mechanical thermal analysis. The mechanical properties of the original and naphthoylated polymers were measured from 25 to 125°C. The results obtained indicate that naphthoylation enhances the tensile properties of the polymers at elevated temperatures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1289–1295, 2003     

Preparation and characterization of amphiphilic block copolymer of polyacrylonitrile‐block‐poly(ethylene oxide)

The synthesis of polyacrylonitrile‐block‐poly(ethylene oxide) (PAN‐b‐PEO) diblock copolymers is conducted by sequential initiation and Ce(IV) redox polymerization using amino‐alcohol as the parent compound. In the first step, amino‐alcohol potassium with a protected amine group initiates the polymerization of ethylene oxide (EO) to yield poly(ethylene oxide) (PEO) with an amine end group (PEO‐NH₂), which is used to synthesize a PAN‐b‐PEO diblock copolymer with Ce(IV) that takes place in the redox initiation system. A PAN‐poly(ethylene glycol)‐PAN (PAN‐PEG‐PAN) triblock copolymer is prepared by the same redox system consisting of ceric ions and PEG in an aqueous medium. The structure of the copolymer is characterized in detail by GPC, IR, ¹H‐NMR, DSC, and X‐ray diffraction. The propagation of the PAN chain is dependent on the molecular weight and concentration of the PEO prepolymer. The crystallization of the PAN and PEO block is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1753–1759, 2003     

Synthesis and characterization of poly[(butylene succinate)‐co‐(butylene terephthalate)]‐b‐poly(tetramethylene glycol) segmented block copolymer

Polyester‐polyether segmented block copolymers of poly[(butylene succinate)‐co‐poly(butylene terephthalate)] (PBS–PBT) and poly(tetramethylene glycol) (PTMG) (M_n = 2000) with various compositions were synthesized. PBT content in the PBS was adjusted to ca. 5 mol %. Their thermal and mechanical properties were investigated. In the case of copolymer, the melting point of the PBS–PBT control was 107.8°C, and the melting point of the copolymer containing 70 wt % of PTMG was 70.1°C. Crystallinity of soft segment was 5 ∼ 17%, and that of hard segment was 42 ∼ 59%. The breaking stress of the PBS–PTMG control was 47 MPa but it decreased with increasing PTMG content. In the case of copolymer containing 70 wt % of PTMG, breaking stress was 36 MPa. Contrary to the decreasing breaking stress, breaking strain increased from 300% for PBS–PBT control to 900% for a copolymer containing 70 wt % of PTMG. The shape recovery ratios of the copolymer containing 70 wt % PTMG were almost twice of those of copolymers containing 40 wt % PTMG. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2067–2075, 2001     

Dynamic mechanical properties of polystyrene‐block‐poly[ethylene‐co‐(ethylene‐propylene)]‐block‐polystyrene triblock copolymer/hydrocarbon oil blends

Blend systems of polystyrene‐block‐poly(ethylene‐co‐(ethylene‐propylene))‐block‐polystyrene (SEEPS) triblock copolymer with three types of hydrocarbon oil of different molecular weight were prepared. The E″ curves as a function of temperature exhibited two peaks; one peak at low temperature (? ?50°C), arising from the glass transition of the poly[ethylene‐co‐(ethylene‐propylene)] (PEEP) phase and a high temperature peak (? 100°C), arising from the glass transition of the polystyrene (PS) phase. The glass transition temperature (T_g) of the PEEP phase shifted to lower temperature with increasing oil content. The shifted T_g depended on the types of oil and was lower for the low molecular weight oil. The T_g of PS phase of the present blend system, were found to be constant and independent of the oil content, when molecular weight of the oil is high. However, for the lower molecular weight oil, the T_g of the PS phase also shifted to lower temperatures. This fact indicates that the oil of high molecular weight is merely dissolved in the PS phase. The E′ at (75°C, at which temperature both of PEEP and PS phases are in glassy state, was found to be independent of oil content. In contrast, at 25°C, at which temperature the PEEP phase is in rubbery state, the E′ decreased sharply with increasing oil content. This result indicates that the hydrocarbon oil was a selective solvent in the PEEP phase. It mainly dissolved in the PEEP phase, although slightly dissolved into the PS phase as well, when molecular weight of oil is low. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Block copolymer formation from the melt reaction between polycarbonate and poly(ethylene‐co‐butylene) diol

The block copolymer formation from the exchange reaction between polycarbonate (PC) and poly(ethylene‐co‐butylene) diol (POH) occurring during melt mixing was studied. The exchange reaction proceeded by the attack of active chain ends of hydroxyl‐terminated POH on the inner carbonate groups of PC. The reaction was accelerated in basic condition in the presence of a hindered amine. The formation of block copolymer was confirmed by ¹H–NMR analysis. The proceeding of the exchange reaction was analyzed with UV spectrometry by measuring the absorbance at 285 nm of the less‐reactive phenolic end group of PC oligomers produced. The reaction was terminated when the hydroxyl end groups of POH were completely consumed. It was found from the analyses by GPC and DSC that the exchange reaction between PC and POH takes place rather uniformly by random scission of the chain. The block copolymer obtained here will be employed as a compatibilizer of PC/polyolefin blends in a future study. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1725–1732, 2001     

用于润滑油改性的乙丙共聚物的合成

以V-A1体系为催化剂,己烷为溶剂,采用分子量调节剂合成出了组成、结构、分子量及分子量分布与美国Exxon-8921基本相同的润滑油改性用乙丙共囊物。经应用评定证明其综合性能好,适合调制各种中、高档多级内燃机油。并在2万t／aEPDM生产装置上实现工生化。     

Preparation and characterization of syndiotactic polystyrene/ethylene‐propylene copolymer blends

The reactive compatibilization of syndiotactic polystyrene (sPS)/oxazoline‐styrene copolymer (RPS)/maleic anhydride grafted ethylene‐propylene copolymer (EPR‐MA) blends is investigated in this study. First, the miscibility of sPS/RPS blends is examined by thermal analysis. The cold crystallization peak (T_cc) moved toward higher temperature with increased PRS, and, concerning enthalpy relaxation behaviors, only a single enthalpy relation peak was found in all aged samples. These results indicate that the sPS/RPS blend is miscible along the various compositions and RPS can be used in the reactive compatibilization of sPS/RPS/EPR‐MA blends. The reactive compatibilized sPS/RPS/EPR‐MA blends showed finer morphology than sPS/EPR‐MA physical blends and higher storage modulus (G') and complex viscosity (η*) when RPS contents were increased. Moreover, the impact strength of sPS/RPS/EPR‐MA increased significantly compared to sPS/EPR‐MA blend, and SEM micrographs after impact testing show that the sPS/RPS/EPR‐MA blend has better adhesion between the sPS matrix and the dispersed EPR‐MA phase. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2084–2091, 2002     

Effects of star‐shaped poly(alkyl methacrylate) arm uniformity on lubricant properties

Star‐shaped poly(alkyl methacrylate)s (PAMAs) were prepared and blended into an additive‐free engine oil to assess the structure–property relationship between macromolecular structure and lubricant performance. These additives were designed with a comparable number of repeating units per arm and the number of arms was varied between 3 and 6. Well‐defined star‐shaped PAMAs were synthesized by atom transfer radical polymerization (ATRP) via a core‐first strategy from multi‐functional head‐groups. Observations of the polymer‐oil blends suggest that stars with less than four arms are favorable as a viscosity index improver (VII), and molecular weight dominates viscosity‐related effects over other structural features. Star‐shaped PAMAs, as oil additives, effectively reduce the friction coefficient in both mixed and boundary lubrication regime. Several analogs outperformed commercial VIIs in both viscosity and friction performance. Increased wear rates were observed for these star‐shaped PAMAs in the boundary lubrication regime suggesting pressure‐sensitive conformations may exist. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43611.     

Synthesis and microphase separation of polystyrene‐b‐polylactide block copolymers aimed at preparation of ordered nanoparticle/block copolymer hybrid materials

A new nanoparticle/block copolymer (NP/BCP) hybrid material combining the unique properties of BCP poly(styrene)‐b‐poly(d ‐lactide) (PS‐b‐PDLA) and inorganic NP quantum dots CdSe was developed. A systematic study on the microphase separation of a series of PS‐b‐PDLAs by small‐angle X‐ray scattering showed that the degree of order of the separated microdomains depended on the initial state of the BCP and the measurement temperature and can be improved through isothermal crystallization of PDLA, thermal annealing and shear field etc. Incorporating a small amount of NPs into the BCP matrix can improve the mobility of the polymer chains and thus promote self‐assembly of the BCP, which leads to hierarchically ordered structures. Excess NPs, however, cannot be completely incorporated into the PDLA domains, resulting in the phase transformation of the BCP, destruction of the ordered structure and even macroscopic phase separation due to the aggregation of NPs. An important observation is that stereocomplexation between PDLA and poly(l ‐lactide) could provide a driving force to promote microphase separation of the BCP. The strategy presented in the current work has potential applications for developing highly ordered NP/BCP hybrid materials. © 2014 Society of Chemical Industry     

Characterization of polystyrene‐b‐poly(ethylene oxide) diblock copolymer and investigation of its micellization behavior in water

The recent studies deal with a diblock copolymer, polystyrene–poly(ethylene oxide). Infrared spectroscopy, proton resonance spectroscopy (¹H‐NMR), and laser light scattering techniques have been used to characterize the polymer. It has been concluded that the sample investigated is diblock copolymer polystyrene–poly(ethylene oxide) having molecular mass 1.656 × 10⁴ g/mol and blocks ratio 1 : 2. The micellization behavior is explored through ¹H‐NMR, laser light scattering, light absorption, surface tension, and conductance and viscosity measurements. The results conclude that the critical micelles concentration of copolymer is 0.0951 g/dL at 25°C. It has been observed that the surface tension of solution decreases with the temperature and its impact is maxima in dilute concentration region. In addition, new methodologies have been introduced to get accurate critical micelles concentration and critical micelles temperature. © 2010 Wiley Periodicals, Inc., J Appl Polym Sci, 2010     

Synthesis and characterization of poly(butylene terephthalate)‐co‐poly(butylene succinate)‐block‐poly(ethylene glycol) segmented block copolymers

Poly(butylene terephthalate)‐co‐poly(butylene succinate)‐block‐poly(ethylene glycol) segmented random copolymers, with poly(butylene succinate) (PBS) molar fraction (M_PBS) varying from 10 to 60 %, were synthesized through a melt polycondensation process and characterized by means of GPC, NMR, DSC and mechanical testing. The number‐average relative molecular mass of the copolymers was higher than 4 × 10⁴ g mol^?1 with polydispersity below 1.9. Sequence distribution analysis on the two types of hard segments by means of ¹H NMR revealed that the number‐average sequence length of PBT decreased from 2.80 to 1.23, while that of PBS increased from 1.27 to 4.76 with increasing M_PBS. The random distribution of hard segments was also justified because of the degree of randomness around 1.0. Micro‐phase separation structure was verified for the appearance of two glass transition temperatures and two melting points, respectively, in DSC thermograms of most samples. The crystallinity of hard segments changed with the crystallizability controlled by the average sequence length and reached the minimum value at an M_PBS of about 50–60 mol%. The results can also be ascribed to the co‐crystallization between two structurally analogous hard segments. Mechanical testing results demonstrated that incorporating a certain amount of PBS moieties (less than 30 mol%), at the expense of a minute depression of the elastic modulus, that higher relative elongation and more flexibility of polymer chain could be expected. Maximum equilibrium water absorption and faster degradation rates were observed on samples with higher M_PBS values and lower crystallinity of hard segments were better hydrophilicity of the polymer chain, through in vitro degradation experiments. Copyright © 2003 Society of Chemical Industry     

Preparation and characterization of a type of ladder‐like poly(phenyl silsesquioxane) based hybrid star‐shaped copolymer of ε‐caprolactone

Combination of the organic–inorganic hybrid such as silsesquioxane with ε‐caprolactone will lead to materials expected to be environmentally friendly and applicable to biomedical usages. A ladder‐like poly(phenyl silsesquioxane) based hybrid star‐shaped copolymer of ε‐caprolactone was prepared by ring opening polymerization of ε‐caprolactone catalyzed by Sn(Oct)₂ with hydroxyl terminated ladder‐like poly(phenyl silsesquioxane) as initiator. The copolymers were characterized by proton nuclear magnetic resonance (¹H‐NMR), silicon nuclear magnetic resonance (²⁹Si‐NMR), Fourier‐transform infrared spectrometer (FT‐IR), size exclusion chromatography (SEC), thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC) in detail. Furthermore, the enzymatic degradation property of the copolymers was also investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42335.     

Nanostructured polymer blends based on polystyrene‐b‐polybutadiene‐b‐poly(methyl methacrylate) triblock copolymers modified with polystyrene and/or poly(methyl methacrylate) homopolymers

Morphologies of polymer blends based on polystyrene‐b‐ polybutadiene‐b ‐poly(methyl methacrylate) (SBM) triblock copolymer were predicted, adopting the phase diagram proposed by Stadler and co‐workers for neat SBM block copolymer, and were experimentally proved using atomic force microscopy. All investigated polymer blends based on SBM triblock copolymer modified with polystyrene (PS) and/or poly(methyl methacrylate) (PMMA) homopolymers showed the expected nanostructures. For polymer blends of symmetric SBM‐1 triblock copolymer with PS homopolymer, the cylinders in cylinders core?shell morphology and the perforated lamellae morphology were obtained. Moreover, modifying the same SBM‐1 triblock copolymer with both PS and PMMA homopolymers the cylinders at cylinders morphology was reached. The predictions for morphologies of blends based on asymmetric SBM‐2 triblock copolymer were also confirmed experimentally, visualizing a spheres over spheres structure. This work presents an easy way of using PS and/or PMMA homopolymers for preparing nanostructured polymer blends based on SBM triblock copolymers with desired morphologies, similar to those of neat SBM block copolymers. © 2017 Society of Chemical Industry     

Tin‐coupled star‐shaped block copolymer of styrene and butadiene (II) properties and application

A novel tin‐coupled star‐shaped block copolymer (SB‐B)₄Sn was synthesized by anionic polymeric techniques. This new copolymer exhibited two different types: One was star‐shaped polybutadiene‐b‐poly(butadiene‐ran‐styrene) (S‐PB‐PSB), and the other was star‐shaped polybutadiene‐b‐poly(butadiene‐ran‐styrene)‐b‐polystyrene (S‐PB‐PSB‐PS). In this article, properties of (SB‐B)₄Sn were contrasted with that of tin‐coupled star‐shaped random styrene‐butadiene rubber (S‐SBR) and S‐SBR/cis‐BR blend rubbers. Physical property testing results showed that (SB‐B)₄Sn possessed good mechanical properties like S‐SBR. Rheological study indicated that these star‐shaped block copolymers had good processing properties. Rubber processing analyzer (RPA) spectra showed that the dispersion of additives in (SB‐B)₄Sn and S‐SBR/cis‐BR blend rubber was much better than that in S‐SBR. Dynamic mechanical thermal analyzer (DMTA) spectra showed that (SB‐B)₄Sn had a good combination of low rolling resistance and high wet skid resistance, which made it satisfactory materials to produce high performance tire tread. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and properties of poly(methyltrifluoropropylsiloxane‐b‐imide) copolymer. I

Poly(methyltrifluoropropylsiloxane‐block‐imide) copolymers (PSBPI), containing various contents of fluorosiloxane, were prepared by the thermal imidization of 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), 4,4′‐oxydianiline (ODA), and α,ω‐aminopropyl‐terminated poly(methyltrifluoropropylsiloxane) prepolymer (APMFS). APMFS was prepared from an equilibrium polymerization of (3,3,3‐trifluoropropyl)methylcyclotrisiloxane (D₃^{Me,CH2,CH2,CF3}) with 1,3‐bis(3‐aminopropyl)‐1,1,3,3‐tetramethyldisiloxane in the presence of the tetramethylammoniumhydroxide (TMAH) catalyst. The content of APMFS, in the reaction mixture, was varied from 0 to 30 wt % of diamine. The structure of copolymer was confirmed by FTIR spectroscopy. The thermal stability, linear coefficient of thermal expansion, modulus, X‐ray pattern, and other properties, such as surface enrichment behavior and solubility, were investigated. PSBPI exhibited relatively low crystallinity regardless of the APMFS content in the copolymer. On the other hand, thermogravimetric, thermomechanical, dynamic mechanical, and surface properties were affected by the content of APMFS segment in the copolymer backbone. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2867–2874, 2002     

Synthesis and characterization of biodegradable block copolymers of poly(propylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol) and poly(ethylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol)

The synthesis of two low molecular weight linear unsaturated oligoester precursors, poly(propylene fumarate‐co‐sebacate) (PPFS) and poly(ethylene fumarate‐co‐sebacate) (PEFS), are described. PPFS, PEFS, and poly(ethylene glycol) are then used to prepare poly(propylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol) (PPFS‐co‐PEG) and poly(ethylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol) (PEFS‐co‐PEG) block copolymers. The products thus obtained are investigated in terms of the molecular weight, composition, structure, thermal properties, and solubility behavior. A number of design parameters including the molecular weights of PPFS, PEFS, and PEG, the reaction time in the polymer synthesis, and the weight ratio of PEG to PPFS or to PEFS are varied to assess their effects on the product yield and properties. The hydrolytic degradation of PPFS‐co‐PEG and PEFS‐co‐PEG in an isotonic buffer (pH 7.4, 37°C) is investigated, and it is found that the fumarate ester bond cleaves faster than does the sebacate ester bond. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 295–300, 2004     

Synthesis of star‐shaped poly(ε‐caprolactone)‐b‐poly(L‐lactide) copolymers: From star architectures to crystalline morphologies

Hexa‐armed star‐shaped poly(ε‐caprolactone)‐block‐poly(L ‐lactide) (6sPCL‐b‐PLLA) with dipentaerythritol core were synthesized by a two‐step ring‐opening polymerization. GPC and ¹H NMR data demonstrate that the polymerization courses are under control. The molecular weight of 6sPCLs and 6sPCL‐b‐PLLAs increases with increasing molar ratio of monomer to initiator, and the molecular weight distribution is in the range of 1.03–1.10. The investigation of the melting and crystallization demonstrated that the values of crystallization temperature (T_c), melting temperature (T_m), and the degree of crystallinity (X_c) of PLLA blocks are increased with the chain length increase of PLLA in the 6sPCL‐b‐PLLA copolymers. On the contrary, the crystallization of PCL blocks dominates when the chain length of PLLA is too short. According to the results of polarized optical micrographs, both the spherulitic growth rate (G) and the spherulitic morphology are affected by the macromolecular architecture and the length of the block chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010