The preparative method of giant single crystals of PEO and the experimental results of them by x-ray diffraction and electron microscopy are described. The crystallization of PEO was carried out in a two dimensional crystallization apparatus. From the tridirectional x-ray diffraction patterns on the resulting platelike crystals, it was confirmed that these crystals have a single crystal-like orientation at high supercoolings, the [401] axis is parallel to a growing direction and the [001] axis is perpendicular to the wide surface, and a double orientation at low supercoolings, two axes of [421] and [421] are parallel to a growing direction and the [001] axis is perpendicular to the wide surface

Monobe, Kazuo

Yamashita, Yuhiko

Okayama University Scientific Achievement Repository

MEMOIRS OF THE SCHOOL OF ENGINEERING, OKAYAMA UNIVERSITY, Vol. 2, No.1, APRIL, 1967Giant Single Crystals of Poly (ethylene oxide)Kazuo MONOBE and Yuhiko YAMASHITADepartment of Industrial Chemistry(Received December 28, 1966)The preparative method of giant single crystals of PEO and the experimentalresults of them by x-ray diffraction and electron microscopy are described. Thecrystallization of PEO was carried out in a two dimensional crystallization appa-ratus. From the tridirectional x-ray diffraction patterns on the resulting plate-like crystals, it was confirmed that these crystals have a single crystal-like orienta-tion at high supercoolings, the [401] axis is parallel to a growing direction andthe [001] axis is perpendicular to the wide surface, and a double orientation atlow supercoolings, two axes of [421] and [421J are parallel to a growing direc-tion and the [001] axis is perpendicular to the wide surface.§ 1. IntroductionVarious high polymers have been obtained inthe form of single crystals in which the molecu-lar chains are folded in segments of 100Asince the polyethylene single crystal wasdiscovered in 19571- 3). Notwithstanding theintrinsic interest of these crystals, much ofcurrent work is, nevertheless, concerned withthe morphology and the structure on thesecrystals with electron microscopy4). The inves-tigation of the mechanical properties on thesecrystals may ultimately lead us to a compre-hension of the situation in bulk polymers. How-ever, their dimensions are too small to examinethem. Furthermore, the structural investiga-tion of single crystals by means of x-ray, in-frared, nmr and other techniques is also con-fronted with the handicap of their smallness.In order to remove this handicap we attemptedto prepare giant single crystals employing thenature of spherulite growth in polymer andsucceeded by moving thin molten sample ofPEO placed between two pieces of glass in asteep temperature slope toward lower tempera-ture at constant speed.The present paper shows the preparativemethod of giant single crystals of PEO and theresults of our studies on them by x-ray diffrac-tion and electron microscopy.§ 2. Principle for Preparation of GiantSingle CrystalsFujiwara's criented crystallization method5)was improved in order to obtain giant singlecrystals of PEO. The crystallization was carried84out in a two dimensional crystallization appa-ratus with a steep temperature slope. Fig. 1shows a thin molten sample placed between twopieces of glass moving with velosity V m awayfrom melt region to crystallization region, ai:'".<::;:--o'"~I------,'--+---l!"-::-c'0clrL-_--I---'--+-__-'-t_Cooling part Healing pari!~DistanceFig. 1 Schematical representation of principlefor preparation of giant single crystals.typical curve for radial growth rate v0 of spheru-lites in crystalline polymer and a temperatureslope between heating part and cooling part. Ifa nucleus forms at A region, the crystallizationwill then proceed in all directions. The crystal-line boundary on the left side will move to theleft at a speed (Vm+Vo) and when Vo has fallento a negligible value, the crystallization willstop. However, on the right side the crystallineboundary will move to the left at a speed (V/It-Ciant Single Crystals of Poly (ethylene oxide)(a)wIde aurfaceplanex-raybeam(b) (c'Fig. 2 Tridirectional x-ray diffraction patterns of the plate-like crystal formed at a movingspeed 0.01 mm. Imin.(a) X-ray beam parallel to a growing direction. A wide surface plane horizontal.(b) X-ray beam perpendicular to a growing direction and a wide surface plane.A growing direction vertical.(c) X-ray beam perpendicular to a growing direction and paraillel to a wiele surfaceplane. A growing direction vertical.86 K. MONOBE and Y. YAMASHITA (Vol. 2,8 thooyerI.( 421)o. ,/~~:-="-:_:c-:...~..T.. -co.,.'d."--...:c-:..-c.,:-7£-----9':/44 t h.loyerFig. 3 Schematical representation of the plate-like crystal and its corresponding reciprocallattice. The reciprocal lattice represents con-veniently the 0, 4 and 8th. layers containingmain reflections.diffraction patterns of the plate-like crystalformed at a moving speed 0.01 mm. Imin. withthe beams (Ni-filtered CuKa radiation) parallelto three mutually perpendicular directions. Thex-ray diffraction pattern shown in Fig. 2 (a) wastaken on a sample so held that the wide surfaceplane was horizontal with the x-ray beam parallelto a growing direction. If the plate-like crystalpossesses a rotation axis along a moving direc-tion, the pattern will not exhibit the arcs orspots as shown in Fig. 2 (a), but only the ringpattern. The indices of the main reflections ofthe pattern, in Fig. 2 are asigned reasonably bythe monoclinic crystal structure proposed forPEa by Tadokoro et aI8). From these tridirec-tional x-ray diffraction patterns it can readily beconcluded with the aid of the reciprocal latticethat the plate-like crystal has a double orienta-tion, tWJ axes of [421J and [421J are parallelto a growing direction and the [OOlJ axis areperpendicular to the wide surface. A closerverification for this conclusion is obtained bystudying the reflections individually, the (120)reflections providing the clearest evidence. InFig. 2 (a) two (120) reflections are in equater, inFig. 2 (c) two (120) reflections are in meridianand in Fig. 2 (b) the intensities of all four (120)reflections are equal, which mean that the re-ciprocal lattice is corresponded for the crystalas shown in Fig. 3. Other reflections can be alsointerpreated by this asignment for the crystal.However, it should be noted that a spread ofeach reciprocal lattice point has been occurredwith a small disturbance of orientation.§ 3. ExperimentalThe samples of PEa used in this study wereCarbowax 6000 (The Carbide and CarbonChemical Company). By the above mentionedmethod, plate-like crystals, 1 mm. in thickness,20 mm. in width and 30 mm. in length, wereproduced for various values of a moving speedranging from 0.008 mm./min. to 1 mm./min.The resulting samples were studied by x-raydiffaction and the fracture surfaces of thesamples were also examined by electron micro-scope using the standard replication.Ve) and when the boundary reaches D, V m = Veand a steady state will be achieved. If the ini-tial nucleus forms at B region where V e is largerthan vm , then on the right side the crystallineboundary will move to the right with a speed(vo-vm) until the boundary reaches D, when asteady state will again be achieved. On theother hand, if an initial nucleus forms at C re-gion, no position of stability can be reached.Therefore, if the initial nucleus forms at A orB region, a single giant spherulite originatesfrom one nucleus and the type of texture whichwould result from this form of growth showsperfect orientation of spherulite radius parallelto the axis of the moving direction. If suchspherulites are parallel in one line, the wholesample will possess the same structure. It isknown6) that the fibril twisting along a radiusoccurs in PEa spherulites as in other polymers.However, if the lamellar width of fibrils islarger than the sample thickness, lamellar sur-faces will be parallel to the glass surfaces. Thatis, the molecular chains will be perpendicularto the wide surface plane of the sample. In sucha principle we have obtained a giant singlecrystal of PEa.§ 4. Results and DiscussionX-ray diffraction patterns on the resultingplate-like crystals confirmed that these crystalshave a single crystal-like orientation at highsupercoolings and a double orientation contain-ing twin structure at low supercoolings. Thefacts that these two type crystals are forme::l atdifferent supercoolings are consistent with ourprevious results7l in PEa spherulites, that is, agrowing direction (a moving direction) possessesa [401J axis below 50°C and two axes of [421Jand [421] above 50°C. Fig. 2 illustrates x-ray1967) Giant Single Crystals of Poly (ethylene oxide)/,Fig. 4 Electron micrograph of fracture surface of the plate-like crystal.87X-ray diffraction studies on the crystals pre-pared with a high moving speed also concludedthat the plate-like cry"tal has a single crystal-like orientation, the [401J axis are parallel t)a growing direction and the [OOlJ axis are per-pendicular to the wide surface.Electron micrograph of fracture surfaces ofthese crystals is shown in Fig. 4. This showsthe texture of the crystal composed of parallellamellae which grow to one direction. There-fore, this observation is an additional support-ing evidence for x-ray diffraction studies.Employing the nature of polymer spherulitegrowth, we succeeded in preparing a giantsingle crystal or a double oriented crystal ofPEO and give the confirmations on their orienta-tion by the use of x-ray diffraction and electronmicroscopy. These crystals are accommodatedwith the studies of various physical propertieson the con trary of tiny single crystals obtainedfrom the solution. Therefore, it is very valuablethat the above mentioned principle for prepara-tion of giant single crystals is applied to otherpolymers. Basing on this concept, experimentsfor the application to other polymers are goingon in our laboratory.AcknowledgmentsThe authors gratefully acknowledge thefinancial support of Fuji Photo. Film Co., Ltd.References1) P. H. TILL: ]. Polymer Sci., 24, (1957) 30l.2) A. KELLER: Phil. Mag. [8J, 2, (1957) 17l.3) E. W. FISCHER: Z. Naturfol·sch .• 12a, (1957) 753.4) P. H. GEIL: Polymer Single Crystals, Inter-science (Wiley), New York, (1963).5) Y. FUJIWARA: ]. Appl. Polymer Sci., 4, (1960)10.6) F. J. BALTA CALLEJA, 1. L. HAY and A. KELLER:Kolloid-Z. und Z. Polymel'e, 209, (1966) 128.7) Y. YAMASHITA and K. MONOBE: This Memoirs,1, (1966) 59.8) H. TADOKORO, Y. YOSHIHARA, S. TAHARA andS. MURAHASHI: Makromol. Chem., 73, (1964) 285.

Giant Single Crystals of Poly (ethylene oxide)

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