三种豆科灌木对干旱胁迫的响应与适应

干旱胁迫是全球范围内影响植物生存、生长和分布的重要环境因子。岷江上游干旱河谷区，由于生态环境的脆弱性和长期人类活动的干扰和过度利用，导致植被严重退化，水土流失加剧，山地灾害频繁，干旱化和荒漠化趋势明显。这种趋势若不能遏制，将严重阻碍区域社会经济的快速协调发展，并且威胁成都平原地区的发展和长江中下游地区的生态安全。因而开展干旱河谷生态恢复研究成为解决这些问题的关键。水分匮乏是限制干旱河谷生态恢复的关键因子，在全球气候变化的背景下，干旱胁迫在区域尺度上可能会更加严重，并使干旱河谷的生态环境更加恶化。因此，深入研究干旱河谷乡土植物对干旱胁迫的响应和适应机理，具有非常重要的理论和实践意义。 本论文以岷江上游干旱河谷的三种乡土豆科灌木，白刺花（Sophora davidii）、小马鞍羊蹄甲（Bauhinia faberi var. microphylla）和小雀花（Campylotropics polyantha）理论和实践意义。为研究对象，在人工控制条件下设计了4-5个连续性干旱胁迫处理，系统地研究了灌木幼苗的生长、生物量积累和水分利用效率（WUE）、形态结构和生理过程等对干旱胁迫的反应，揭示了幼苗的干旱适应能力及种间差异。主要研究结论如下： 1) 灌木生长和繁殖对干旱胁迫的反应 在干旱胁迫下，幼苗生长速率显著减小，叶片衰老和脱落比率增大，这些变化随着胁迫强度的增加具有累积效应。叶片比茎对干旱胁迫的反应更敏感。在严重干旱胁迫下，幼苗的有性繁殖被限制，但在中等程度干旱胁迫下，幼苗的有性繁殖能力被提高。 2) 灌木生物量积累及其分配和WUE对干旱胁迫的反应 在干旱胁迫下，灌木各器官的生物量都显著减小，但是生物量的分配侧重于地下部分，使得根茎比在干旱条件下增大。幼苗的耗水量（WU）随着干旱胁迫的增加而显著减少。白刺花和小马鞍羊蹄甲WUE在干旱胁迫下降低；小雀花的WUE在中等干旱胁迫下升高。 3) 灌木叶片结构特征对干旱胁迫反应 白刺花叶片具有较为典型的旱生型结构，而小马鞍羊蹄甲和小雀花则为中生型结构。在1至2年的干旱胁迫下，灌木叶片结构组成未发生本质性的改变，主要是细胞大小的变化。在中等和严重干旱胁迫下，叶肉组织厚度明显减小；并且气孔和表皮细胞面积也显著减小，气孔和表皮细胞密度显著增大；叶肉细胞层数、P/S值、表皮厚度等无显著变化。 4) 灌木对干旱胁迫的生理响应 气体交换参数和叶片相对含水量（RWC）在中等干旱胁迫下发生了明显的改变，而叶绿素荧光参数和光合色素含量在严重干旱胁迫下才发生显著变化。在干旱胁迫下，净光合作用速率（Pn）、气孔导度（gs）和RWC呈下降趋势，而叶片温度（Tl）呈增加趋势，蒸腾速率（Tr）的变化不明显。除了日最大Pn减小以外，干旱胁迫对气体交换参数的日变化无显著影响，但是对光合-光响应曲线有显著的影响，使有效光合时间缩短。在严重干旱胁迫下光系统受到损害而代谢减弱，PSⅡ中心的内禀光能转换效率（Fv/Fm）、量子产量（Yield）、光化学淬灭参数（qP）显著降低，而非光化学淬灭参数（NPQ）明显增加。气孔限制和非气孔限制对Pn的影响与干旱胁迫强度有关。在中度胁迫下，气孔限制起主导作用，在严重胁迫下非气孔限制起主导作用，40% FC水分条件可能是灌木由气孔限制向非气孔限制的转折点。 5) 灌木对干旱胁迫的适应能力及其种间差异 三种灌木对干旱胁迫具有较好的适应能力，即使在20% FC，幼苗未因干旱胁迫III而死亡；80% FC适宜于幼苗生长。白刺花生长速率慢，耗水量较少，具有较强的耐旱和耐贫瘠能力，并具有干旱忍受机制，能够在较干旱的环境中定居和生长。小马鞍羊蹄甲和小雀花，生长快，水分消耗量较大，尤其是小雀花，对干旱胁迫的忍受能力较弱，具有干旱回避机制，因而适宜于在较为湿润的生境中生长。综合分析表明，生长速率较慢的物种抗旱能力较强，其更适宜于作为干旱地区植被恢复物种。 Drought is often a key factor limiting plant establishment, growth and distribution inmany regions of the world. The harsh environmental conditions and long-termanthropogenic disturbance had resulted in habitat destruction in the dry valley ofMinjiang river, southwest China. Recently, it tended to be more severe on the vegetationdegradation, soil erosion and water loss, natural disaster, as well as desertification, whichimpact on regional booming economy and harmonious development, and would be verydangerous to the environmental security in the middle and lower reaches of Yangzi River.Therefore, ecological restoration in the dry valley is one of the vital tasks in China. Waterdeficit is known to affect adversely vegetation restoration in this place. Moreover, in thecontext of climate change, an increased frequency of drought stress might occur at aregional scale in the dry valleys of Minjiang River. The selection of appropriate plantingspecies for vegetation restoration in regard to regional conditions is an important issue atpresent and in further. The research on responses of indigenous species to drought stresscould provide insights into the improvement of the vegetation restoration in the dry valleys of Minjiang River. In this paper, the responses of three indigenous leguminous shrubs, Sophora davidii,Bauhinia faberi var. microphylla and Campylotropics polyantha, to various soil watersupplies were studied in order to assess drought tolerance of seedlings, and to compare interspecific differences in seedlings’ responses to drought stress. The results were as follows: 1 Growth and reproduction of shrubs in response to drought stress Seedling growth reduced significantly while leaf senescence accelerated underdrought stress, the cumulative responses to prolonged drought were found. The capacityfor reproduction was limited by severe drought stress, and improved by moderate droughtstress. Leaf responses were more sensitive than shoot to various water supplies. 2 WUE, biomass production and its partitioning of shrubs in response to drought stress Drought stress reduced significantly the total dry mass and their components ofseedlings, and altered more biomass allocation to root system, showing higher R/S ratiounder drought. Water use (WU) and water-use efficiency (WUE) of both S. davidii and B.faberi var. microphylla declined strongly with drought stress. The WU C. polyantha ofalso declined with drought stress, but WUE improved under moderate drought stress. 3 Anatomical characteristics and ultrastructures of leaves in response to drought stress There were xeromorphic for S. davidii leaves and mesomorphic for B. faberi var.microphylla and C. polyantha at the all water supplies. The foundational changes in leafstructures were not found with drought stress. However, mesophyll thickness, the areas ofstomatal and epidermis reduced slightly while the densities of stomatal and epidermisincreased under severe drought stress. Variations in these parameters could mainly be duoto cell size. Other structures did not displayed significant changes with drought stress. 4 Physiological responses of shrubs to drought stress The gas exchange parameters and leaf relative water content (RWC) were affectedby moderate stress, while chlorophyll fluorescence and chlorophyll content were onlyaffected by severe stress. Drought stress decreased net photosynthesis rate (Pn), stomatalconductance, light-use efficiency and RWC, and increased leaf temperature. Therespiration rates (Tr) were kept within a narrower range than Pn, resulting in aprogressively increased instantaneous water use effiecency (WUEi) under drought stress.Moreover, drought stress also affected the response curve of Pn to RAR, there was adepression light saturation point (Lsat) and maximum Pn (Pnmax) for moderate andsevere stressed seedling. However, diurnal changes of gas exchange parameters did notdiffer among water supplies although maximum daily Pn declined under severe stress.VISevere stress reduced Fv/Fm, Yield and qP while increased NPQ and chlorophyll content.Photosynthetic activity decreased during drought stress period due to stomatal andnon-stomatal limitations. The relative contribution of these limitations was associatedwith the severity of stress. The limitation to Pn was caused mainly by stomatal limitationunder moderate drought stress, and by the predominance of non-stomatal limitation undersevere stress. In this case, 40% FC water supply may be a non-stomatal limitation 5 Interspecific differences in drought tolerance of shrubs Three shrubs exhibited good performance throughout the experiment process, evenif at 20% FC treatment there were no any seedlings died, 80% FC water supply wassuitable for their establishment and growth. S. davidii minimized their water loss byreducing total leaf area and growth rate, as well as maintained higher RWC and Pncompared to the other two species under drought stress, thus they might be more tolerantto the drought stress than the other two species. On the contrary, it was found that C.polyantha and B. faberi var. microphylla had higher water loss because of their stomatalconductance and higher leaf area ratios. They reduced water loss with shedding theirleaves and changing leaf orientation under drought stress. Based on their responses, thestudied species could be categorized into two: (1) S. davidii with a tolerance mechanismin response to drought stress; (2) C. polyantha and B. faberi var. microphylla withdrought avoidance mechanism. These results indicated that slow-growing shrub speciesare better adapted to drought stress than intermediate or fast-growing species in present orpredicted drought conditions. Therefore, selecting rapid-growing species might leavethese seedlings relatively at a risk of extreme drought.

青杨(Populus cathayana Rehd.)对逆境胁迫的反应及lea基因的表达分析

杨树具有分布广、适应性强，在生态环境治理和解决木材短缺方面均占有重要位置。青杨(Populus cathayana Rehd.)是青杨派树种的重要成员之一，也是我国的特有种。本研究通过对不同水分梯度的干旱胁迫下青杨形态和生理生化的反应，不同pH值盐碱胁迫下不同海拔和不同气候地区的四个青杨种群在生理生态上的反应差异，以及在干旱和低温胁迫下青杨lea2, lea3组基因表达差异的研究，从形态、生理、生化和分子生物学水平系统地研究了青杨在不同逆境胁迫下的反应和青杨不同种群在盐碱胁迫下的反应差异。主要研究结果如下： 1. 青杨在干旱胁迫下的反应机制：中度和重度干旱胁迫下植株的生长受到明显抑制。表现在光合系统上青杨的净光合同化速率(A)下降，主要原因是气孔导度(gs)，胞间二氧化碳浓度(Ci)下降。另外最大量子产量(Fv/Fm)、光化学猝灭效率(qP)降低反应了干旱胁迫下光合系统II(PSII)受到严重损伤, 而且非光化学猝灭效率(qN)上升，导致可利用化学能产量下降，叶绿体产生淀粉的量减少。qP降低qN上升导致产生的过量电子对光合系统的伤害造成活性氧以及丙二醛(MDA)的含量增加。超微解剖结构显示，干旱胁迫增强时，叶绿体内淀粉粒的数目减少，而且叶绿体、线粒体等细胞器中嗜锇颗粒的数目增加。为清除细胞内的活性氧，植物一般的反应是抗氧化系统酶活性增加，对青杨来讲超氧化物歧化酶(SOD), 抗坏血酸过氧化物酶(APx)活性的增加远大于过氧化物酶(POD)，这显示了在青杨中SOD、APx酶在清除活性氧的作用上大于POD。另外同工酶研究结果显示这些酶活性的升高主要是由于各条同工酶带表达量的增加，而不是诱导新酶带的产生。另外，75% FC水分处理下有些指标非但没有下降，像A和有效光量子产量(Y)的值都略有增加，而且gs同时增加。另外，100% FC比75% FC细胞内淀粉粒的数目少一些，但有少量的嗜锇颗粒。这证明100% FC土壤水分也许并非最适合青杨生长。 2. 盐碱胁迫对不同海拔地区青杨种群的反应差异：青杨高海拔和低海拔种群的各种生理特性随着pH值上升都受到了很大的影响。两种群叶和根中Na+、K+ 含量, Na+/K+比率随着pH值的上升影响显著。在pH值高于10.4时高海拔种群叶和根中Na+/K+比率急剧下降但是低海拔种群中却一直维持在较高水平。两种群中MDA、脯氨酸(Proline)的含量，抗氧化系统酶的活性都受到了严重的影响，证明两个种群都属于盐碱胁迫敏感类型但是高海拔的种群对盐碱胁迫的耐性要高于低海拔。这主要是由于高海拔种群一般具有耐干旱、低温胁迫的能力，而植物的抗逆机制一般都有共通之处。 3. 盐碱胁迫对不同气候地区青杨种群的反应差异：盐碱胁迫下两种群的光合作用受到明显的抑制，具体表现在叶绿素的含量和A 显著下降。净光合速率的下降主要是由于叶片gs，Ci 值降低引起的。与湿润地区的种群相比盐碱胁迫增强时，干旱地区的种群叶绿素含量和光合能力的升高与K+离子含量增加有关。植物维持细胞质高K+/Na+值对植物的抗盐性有很重要的作用。为清除盐碱胁迫产生的活性氧，抗氧化系统酶活性增加。盐碱胁迫下干旱地区的种群在SOD、CAT 和谷胱甘肽还原酶(GR)等酶的活性均显著上升，而湿润地区种群只有谷胱甘肽氧化酶(GST)的活性明显增加，说明干旱种群的抗氧化酶系统在较高盐碱胁迫下的保护作用要强于湿润种群。这主要是由于植物抗盐碱胁迫与抗干旱胁迫在一些方面的机制是一致的，抗旱种群一般也能抵抗一定程度的盐碱胁迫。 4. 青杨lea2、lea3 基因在干旱和低温胁迫下的表达差异：通过荧光定量PCR 分析，lea2、lea3 组基因在干旱和低温胁迫下在mRNA 水平的瞬时表达量明显升高，说明了两基因在青杨耐干旱和低温胁迫上都起显著的作用。而且两基因在干旱胁迫下，表达量的升高和降低的时间近乎同步，表明两基因在干旱胁迫下对植物应急保护机制的启动都发挥着重要的作用。低温胁迫下lea3 基因在mRNA 水平上表达量显著上升的时间要早于lea2，而且lea3 基因的持续作用时间明显长于lea2 组基因，说明了低温胁迫开始时lea3基因在植物应对逆境的作用上要大于lea2 基因。 Poplars play an important role in lumber supply, and are important components of ecosystems due to their wide distribution and well adaptation. Populus cathayana Rehd., which belongs to Populus Sect. Tacamahaca Spach, is one of the most important resources of poplars and is specialist to china. In this study, different altitudes and climates populations of P. cathayana were used as experiment materials to investigate the adaptability to drought and salt-alkali stresses. And the cultures of P. cathayana were used to analyze the lea2 and 3 group genes expression when exposed to drought and low temperature stresses. The results are as follows: 1. A large set of parallel responses to drought stress: Drought stress caused pronounced growth inhibition. A decreased significantly and was mainly the result of gs and Ci down. Besides, Fv/Fm, qP decreased and that reflected the harmful effects to PSII of drought stress. In accordance with qN increasing, decreased useful energy production caused the starch numbers reduction in chloroplast. The qP up and qN down improved the levels of ROS and MDA. Starch numbers in chloroplast reduced and plastoglobuli numbers increased when soil water content decreased. To reduce ROS, the activities of SOD, APX, CAT and PPO were activated. The isozymes results show that the rising activities of the antioxidant enzymes resulted from certain isoform content increased, and not from the new band produced. Interestingly, morphological results show 100%FC maybe wasn’t the favorite water content for P. cathayana growth. 2. Effect of salt-alkali stress on morphological and physiological changes in two different altitudes populations of P. cathayana: We compared the physiological responses of two populations of Populus cathayana Rehder, originating from altitudes 2,840 m and 1,450 m. Our results demonstated that Na+ and K+ contents, and Na+/K+ ratios in leaves and roots are greatly affected by pH values. At pH 10.4, the Na+/K+ ratios in both leaves and roots sharply dropped in the higher altitude population but were always maintained at higher levels in the lower altitude population. The pH values causing maximum malondialdehyde (MDA) level, free proline content and antioxidant enzyme activities were significantly different in two populations. These results indicated that the higher altitude population exhibits greater tolerance to alkalinity stress than does the lower altitude population. 3. Morphological and physiological changes in two different climates populations of P. cathayana when exposed to salt-alkali stress. Salt-alkali stress caused pronounced inhibition of the growth and especially in photosystem. Pigments content and A decreased significantly and at the same time gs and Ci decreased too. Compared with wet climate population, the Chlorophyll content and A increased in drought climate population as pH value rising was related to the K+ content increasing. It is important to resist salt-alkali stress that the K+/Na+ ratio matained at high level in cytoplasm. To reduce ROS content, the SOD, CAT and GR activities rised significantly in drought population but only GST increased in wet population. The drought population showed higher salt-alkali tolerance than the wet population mainly resulted from the fact that drought tolerance was in accordance with salt-alkali tolerance to some extent. 4. The different expressional model of lea2 and lea3 gene when P. cathayana was exposed to drought and cold stress. RT-PCR results show both lea2 and lea3 suddenly expressed significantly in mRNA level under drought and cold stress. The expression level of two genes reached optimal level at the same time. But under cold stress, the earlier significantly rising expressional time and the longer maintained higher level time in lea3 than lea2 elucidated that lea3 may be more important than lea2 in resisting cold stress in short time in P. cathayana.

High-spin states of odd-odd nuclei in the A similar to 170 mass region

Efforts have been made in our group to study the band structure of odd-odd nuclei in the A similar to 170 mass region. We aimed at providing new data of high-spin states and searching for the low-spin signature inversion in the 2-qp bands built on the pi h(9/2) circle times nu i(13/2) and pi i(13/2)circle times nu i(13/2) configurations. In this talk, main results of our work will be summarized, and some systematic features of signature inversion discussed. The spin and parity assignments for the pi i(13/2) circle times nu i(13/2) band in (184)An could be regarded as firm providing a good example for systematic and theoretical investigations.

Two-quasiparticle K-isomeric states in strongly deformed neutron-rich Nd and Sm isotopes: a projected shell-model analysis

Motivated by recent spectroscopy data from fission experiments, we apply the projected shell model to study systematically the structure of strongly deformed, neutron-rich, even-even Nd and Sm isotopes with neutron number from 94 to 100. We perform calculations for rotational bands up to spin I = 20 and analyze the band structure of low-lying states with quasiparticle excitations, with emphasis given to rotational bands based on various negative-parity two-quasiparticle (2-qp) isomers. Experimentally known isomers in these isotopes are described well. The calculations further predict proton 2-qp bands based on a 5(-) and a 7(-) isomer and neutron 2-qp bands based on a 4(-) and an 8(-) isomer. The properties for the yrast line are discussed, and quantities to test the predictions are suggested for future experiment.

大气NH_3和介质供氮水平对不同氮效率玉米基因型叶绿素荧光参数的影响

采用开顶式气室(Open Top Chambers)进行水培试验,以两种氮效率玉米(ZeamaysL.)基因型为供试作物,通过不同大气NH3浓度处理,测定苗期各叶绿素荧光动力学参数。结果表明,供氮介质和大气NH3浓度升高对两种氮效率玉米基因型的初始荧光值(Fo)不存在显著影响。高供氮介质下,在NH3浓度升高时,氮高效5号基因型的最大荧光产量(Fm)和可变荧光(Fv)均显著减小(p<0.05),而氮低效基因型四单19的Fm、Fv值显著增加;低供氮介质下,大气NH3浓度升高对2种基因型Fm、Fv值的影响结果与高供氮介质时相反。说明大气NH3浓度升高对生长在高供氮介质下的氮高效5号基因型有一定的抑制作用,而对氮低效基因型四单19有一定程度的促进作用。在不同供氮介质下,大气NH3浓度升高时,两种氮效率玉米基因型的qN、qP值减小,说明大气NH3浓度升高时,作物对光合机构的保护能力比大气背景NH3浓度时弱。

子午岭林区白桦-辽东栎混交林光合生理生态特征研究

对黄土高原子午岭次生林区白桦林、辽东栎林和白桦-辽东栎混交林3种林分的土壤物理特性和叶片光合特性进行了研究。结果表明:(1)白桦-辽东栎混交林地的土壤水分明显改善,其土壤容重最小、土壤孔隙度最大,且均优于纯林,即混交林地有深层次的土壤水分可供利用,并改善了土壤的物理结构;(2)辽东栎林的光合速率和气孔导度最大,其次为白桦-辽东栎混交林,水分利用率(WUE)为混交林白桦>混交林辽东栎>辽东栎林>白桦林;(3)混交林中白桦、辽东栎的Fv/Fm和Fv/Fo值均较大,与纯林差异不显著;白桦林和辽东栎林的qP和NPQ值均大于混交林。

柑橘叶片气孔导度的环境响应模型研究

对柑橘叶片气孔导度的模拟研究结果表明,柑橘叶片气孔导度的环境响应模型中环境变量至少需含有光合有效辐射在内的2个及其以上的环境变量;在温度较适宜的生长季除光合有效辐射外,环境变量对模型精度影响程度依次为饱和水汽压差>叶片温度>空气CO2浓度;在温度和空气CO2浓度变化较大的季节模型精确度则受单一环境变量和变量间交互作用的影响;3月份柑橘叶片气孔导度对环境因子的响应可采用Jarvis模型的G(Qp)g(De)形式,而7月、11月和3～11月份则均可采用G(Qp)g(De)g(Tl)形式描述

Synthesis and fluorescent property of NH4Y1.9Eu0.1F7 nanoparticles with the temperature effect on the morphology

Sphere NH4Y1.9Eu0.1F7 nanoparticles were successfully synthesized by a hydrothermal method at 180 degrees C for 10 h. SEM and TEM images show the particles are spheres and have lots of hollows in them. The mean particle size is about 60 nm. The shape and size of the particles can be controlled by changing temperature and time of reactants. The luminescent property of the sample indicates that strong emission peaks of the Eu3+ ions are located at about 589 and 612 mm.

Phase behavior of polymer blends

The present report deals with some results on phase behavior, miscibility and phase separation for several polymer blends casting from solutions. These blends are grouped as the amorphous polymer blends, blends containing a crystalline polymer or two crystalline polymers. The blends of PMMA/PVAc were miscible and underwent phase separation at elevated temperature, exhibited LCST behavior. The benzoylated PPO has both UCST and LCST nature. For the systems composed of crystalline polymer poly(ethylene oxide) and amorphous polyurethane, of two crystalline polymers poly(epsilon-caprolactone) and poly[3,3,-bis-(chloromethyl) oxetane], appear a single T-g, indicating these blends are miscible. The interaction parameter B's were determined to be -14 J cm(-3), -15 J cm(-3) respectively. Phase separation of phenolphthalein poly(ether ether sulfone)/PEO blends were discussed in terms of thermal properties, such as their melting and crystallization behavior.

Miscibility and phase behavior in blends containing random copolymers of poly(ether ether ketone) and phenolphthalein poly(ether ether ketone)

The miscibility and phase behavior of polysulfone (PSF) and poly(hydroxyether of bisphenol A) (phenoxy) with a series of copoly(ether ether ketone) (COPEEK), a random copolymer of poly(ether ether ketone) (PEEK), and phenolphthalein poly(ether ether ketone) (PEK-C) was studied using differential scanning calorimetry. A COPEEK copolymer containing 6 mol % ether ether ketone (EEK) repeat units is miscible with PSF, whereas copolymers containing 12 mol % EEK and more are not. COPEEK copolymers containing 6 and 12 mol % EEK are completely miscible with phenoxy, but those containing 24 mol % EEK and more are immiscible with phenoxy. Moreover, a copolymer containing 17 mol % EEK is partially miscible with phenoxy; the blends show two transitions in the midcomposition region and single transitions at either extreme. Two T(g)s were observed for the 50/50 blend of phenoxy with the copolymer containing 17 mol % EEK, whereas a single composition-dependent T-g appeared for all the other compositions. An FTIR study revealed that there exist hydrogen-bonding interactions between phenoxy and the copolymers. The strengths of the hydrogen-bonding interactions in the blends of the COPEEK copolymers containing 6 and 12 mol % EEK are the same as that in the phenoxy/PEK-C blend. However, for the blends of copolymers containing 17, 24, and 28 mol % EEK, the hydrogen-bonding interactions become increasingly unfavorable and the self-association of the hydroxyl groups of phenoxy is preferable as the content of EEK units in the copolymer increases. The observed miscibility was interpreted qualitatively in terms of the mean-field approach. (C) 1996 John Wiley & Sons, Inc.

MISCIBILITY AND PHASE-BEHAVIOR IN BLENDS OF POLY(HYDROXYETHER OF BISPHENOL-A) WITH POLY(ETHYLENE OXIDE-CO-PROPYLENE OXIDE)

The miscibility of poly(hydroxyether of bisphenol A) (phenoxy) with a series of poly(ethylene oxide-co-propylene oxide) (EPO) has been studied. It was found that the critical copolymer composition for achieving miscibility with phenoxy around 60-degrees-C is about 22 mol % ethylene oxide (EO). Some blends undergo phase separation at elevated temperatures, but there is no maximum in the miscibility window. The mean-field approach has been used to describe this homopolymer/copolymer system. From the miscibility maps and the melting-point depression of the crystallizable component in the blends, the binary interaction energy densities, B(ij), have been calculated for all three pairs. The miscibility of phenoxy with EPO is considered to be caused mainly by the intermolecular hydrogen-bonding interactions between the hydroxyl groups of phenoxy and the ether oxygens of the EO units in the copolymers, while the intramolecular repulsion between EO and propylene oxide units in the copolymers contributes relatively little to the miscibility.

CRYSTALLIZATION OF RARE-EARTH OXIDE-FILLED POLYPROPYLENE

A study has been made of the crystallization behavior of polypropylene (PP) filled with rare earth oxides under isothermal conditions. These rare earth oxides include lanthanum oxide (La2O3), yttrium oxide (Y2O3), and a mixture of rare earth oxides containing 70% Y2O3 (Y2O3-0.70). A differential scanning calorimeter was used to monitor the energetics of the crystallization process from the melt. During isothermal crystallization, dependence of the relative degree of crystallinity on time was described by the Avrami equation. It has been shown that the addition of any of the three rare earth oxides causes a considerable increase in the overall crystallization rate of PP but does not influence the mechanism of nucleation and growth of the PP crystals. The analysis of kinetic data according to nucleation theories shows that the increase in crystallization rate of PP in the composites is due to the decrease in surface energy of the extremity surfaces. The relative contents of the beta-form in the composites are somewhat higher than that in the plain PP. However, the contents of the beta-form in the plain PP and the composites are all very low relative to those of the alpha-form and the influence of the formation of the beta-form on the crystallization kinetics can be neglected.

MISCIBILITY OF POLY(HYDROXYETHER OF PHENOLPHTHALEIN) WITH POLY(ETHER SULFONE)

Blends of poly(hydroxyether of phenolphthalein) (PHP) with poly(ether sulphone) (PES) were prepared by casting from a common solvent; they were found to be miscible and show a single, composition-dependent glass transition temperature. All the PHP/PES blends exhibited lower critical solution temperature behaviour, i.e. phase separation occurred at elevated temperatures. A F.T.-i.r. study revealed that a hydrogen-bonding interaction occurs between these polymers but it is weaker than in pure PHP. The observed miscibility is hence proposed to be the result of specific interactions between the polymers.

BLENDS OF POLY[3,3-BIS(CHLOROMETHYL)OXETANE] WITH POLY(VINYL ACETATE) .1. THERMAL AND MECHANICAL-PROPERTIES

Blends of poly[3,3-bis(chloromethyl)oxetane] (Penton) with poly(vinyl acetate) were prepared. Compatibility, morphology, thermal behavior, and mechanical properties of blends with various compositions were studied using differential scanning calorimetry (DSC), dynamic mechanical measurements (DMA), tensile tests, and scanning electron microscopy (SEM). DMA study showed that the blends have two glass transition temperatures (T(g)). The T(g) of the PVAc rich phase shifts significantly to lower temperatures with increasing Penton content, suggesting that a considerable amount of Penton dissolves in the PVAc rich phase, but that the Penton rich phase contains little PVAc. The Penton/PVAc blends are partially compatible. DSC results suggest that PVAc can act as a beta-nucleator for Penton in the blend. Marked negative deviations from simple additivity were observed for the tensile strength at break over the entire composition range. The Young's modulus curve appeared to be S-shaped, implying that the blends are heterogeneous and have a two-phase structure. This was confirmed by SEM observations.