辐射交联顺1,4-聚丁二烯的NMR研究

用１３Ｃ ＮＭＲ方法,测定了辐射交联顺１,４ 聚丁二烯在室温下的自旋 晶格弛豫时间（Ｔ１）,核Ｏｖｅｒｈａｕｓｅｒ因子（ＮＯＥ）,和１３Ｃ ＮＭＲ线宽．以及凝胶本体１Ｈ ＮＭＲ的Ｔ１和Ｔ２弛豫时间,结果表明,辐射交联顺１,４ 聚丁二烯体系中,随着凝胶含量的增加各碳核质子的Ｔ１值变化很小,而—ＣＨ２—核的ＮＯＥ因子明显降低和１３Ｃ ＮＭＲ线宽增宽．以及１Ｈ ＮＭＲ的Ｔ１和Ｔ２表现的双指数弛豫特性反映了交联体系中大分子链段长程运动受阻以及饱和交联叔碳核—ＣＨ对链段运动的影响．     

HTPB/HDI本体聚合反应动力学研究

用基团分析方法对端羟基聚丁二烯（ＨＴＰＢ）／己二异氰酸酯（ＨＤＩ）体系的本体聚合反应的动力学进行了研究。探讨了催化剂二丁基二月桂酸锡（ＤＢＴＤＬ）对反应速度的影响。结果表明,催化体系的聚合反应速度完全满足双螺杆挤出机反应挤出停留时间的要求。『     

α‐ and β‐Relaxations in neat and antiplasticized polybutadiene

Dielectric spectroscopy was carried out to measure the α‐relaxation (local segmental motion) and the higher frequency, secondary relaxation (β‐mode) in 1,4‐polybutadiene, both neat and containing a nonpolar diluent, mineral oil. The α‐relaxation shifted to lower frequencies (antiplasticization) in the presence of the diluent, suggesting the glass temperature of the latter is higher than the T_g of the polymer (i.e., >187K). The T_g of neat mineral oil cannot be determined directly, due to crystallization. While the diluent increased the magnitude of the α‐relaxation times, it had no effect on the β‐relaxation. Moreover, neither the shape of the α‐relaxation function nor its temperature dependence was influenced by the diluent. From this we conclude that the main effect of the mineral oil was to increase the local friction, without changing the degree of intermolecular cooperativity of the molecular motions. We also find that near the glass temperature, there is rough agreement between the time scale of the secondary relaxation process and the value of a noncooperative relaxation time estimated from theory. This approximate correspondence between the two relaxation times also holds for 1,2 polybutadiene. However, the β‐process cannot be identified with the noncooperative α‐relaxation, and the relationship between them is not quantitative. © 2000 John Wiley & Sons, Inc.* J Polym Sci B: Polym Phys 38: 1841–1847, 2000     

Ultimately Specific 1,4‐cis Polymerization of 1,3‐Butadiene with a Novel Gadolinium Catalyst

Novel complexes [(C₅Me₅)₂Ln][B(C₆F₅)₄] (Ln = Pr, Nd, or Gd) were prepared, which in combination with ⁱBu₃Al efficiently induce highly 1,4‐cis‐specific polymerization of butadiene. The activity of the Gd complex/ⁱBu₃Al system is high enough to exhibit good catalytic activity even at low temperature. Polymerization at −78 °C gave polybutadiene with nearly perfect 1,4‐cis microstructure (>99.9%) with sharp molecular weight distribution (M _w/M _n = 1.45) and in reasonable yield.

ORTEP drawing of 2b . Selected bond distances (Å): Pr‐F1 = 2.549(2), Pr‐F19 = 2.625(2).     

Functionalization of polymers: Epoxidation of polyolefins

In order to produce a polymer with an epoxy group, the epoxidation of the polyolefins poly(ethylene-co-1,9-decadiene) (PED) and polybutadiene (PB) was investigated. For these reactions, in situ generated peroxy acid was most effective and convenient. Among them an H₂O₂–formic acid system gave the best result. The reactivity of PB showed the dependency on the microstructure. The reactivity of the double bond is trans>cis> vinyl(pendant) and the selectivity for the epoxidation is cis∼vinyl(pendant)≫trans.     

Thermodynamic interaction parameter of star–star polybutadiene blends

The value of the thermodynamic interaction parameter, χ_eff, for star–star polybutadiene blends was determined with small‐angle neutron scattering. Blends in which the stars have the same number of arms and blends in which the stars have different numbers of arms are investigated. For star–star isotopic blends with components having the same number of arms, the presence of the junction point of the star leads to a value of χ_eff that is larger than that for an analogous linear–linear isotopic blend. However, changes in the value of χ_eff resulting from small dissimilarities in the number of arms of the two components in the isotopic star–star blends were too small to resolve. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 247–257, 2003     

Moduli of model elastomeric networks prepared from polymer chains having a high plateau modulus,and their interpretation in terms of the constrained-chain model

High-molecular weight polybutadiene chains having approximately 47% cis-1,4 units and 45% trans-1,4 units were crosslinked through their carbon-carbon double bonds using p-bis(dimethylsilyl) benzene as crosslinking agent and chloroplatinic acid as catalyst. This particular polymer was chosen because the high plateau modulus it exhibits in the un-crosslinked state is taken to indicate large numbers of chain entanglements, and stress–strain measurements on such networks have frequently been interpreted with the assumption that the trapping of such entanglements during crosslinking should contribute significantly to their modull. It is shown in the present investigation that such results are equally well interpreted in terms of the new constrained-chain theory of rubbery elasticity. © 1993 John Wiley & Sons, Inc.     

高顺式聚丁二烯的低温红外光谱

在聚丁二烯(PBD)的微结构分析中人们多采用738cm~(-1)吸收带作为顺式结构分析峰,而该吸收带随分子链构象和微结构序列分布的变化却未曾有详细研究。本文考察了高顺式PBD结晶前后的红外光谱变化,特别是738cm~(-1)带的变化,并用分子链构象的变化给予了解释。试样是日本BR-01胶,顺式含量经~(13)C-NMR测定为96.6％,胶样配成约2％的CS_2溶液,在KBr晶片上涂膜,红外灯下除去溶剂,用DIGILAB FTS-20E型红外光谱仪记录光     

Energetic polymers as binders in composite propellants and explosives

The principles behind the use of polymeric binders in composite propellants and explosives are described with emphasis on the properties which they should possess in order to satisfy the requirements for inclusion in a composition. The desirability of using energetic polymers as binders in terms of both performance and safety, and the problems associated with their preparation and properties, are discussed. The contributions of chemical synthesis within DRA to overcome these problems will be shown. Preparation of energetic polymers both by polymer modification and by polymerization of an energetic monomer is described. We have developed three energetic polymers: poly-3-nitratomethyl-3-methyloxetane (polyNIMMO), polyglycidyl nitrate (polyG-LYN) and nitrated hydroxy-terminated polybutadiene (NHTPB). Two of these (polyNIMMO and polyGLYN) have shown excellent properties in propellant and explosive formulations and proved that low-vulnerability, high-performance compositions are possible. The properties of the products from our work are compared with those of other groups and a glimpse of the future in this area is given to show the potential for new energetic polymers.