Fujiwara's oriented crystallization method was applied to poly (ethylene oxide) to obtain a uniform texture composed of parallel fibrils which correspond to the structure of a radial direction of spherulites. Two different x-ray diffraction patterns in crystallite orientation of the spherulite radius were obtained. From these patterns and crystallization conditions it could be determined that the
spherulite radius has a [401] rotation axis below about 50℃ and two [421] and [421]rotation axes above about 50℃.
A reasonable interpretation was given for these two ways of spherulitic crystallization, based on the growth features of lamellar crystals of poly (ethylene oxide). That is, it is concluded that a second order transition in poly (ethylene oxide) lamellar crystals near the temperature of 50℃ is responsible for the change of the rotation axis in spherulite radius

Monobe, Kazuo

Yamashista, Yuhiko

Yokoyama, Fumiyoshi

English

Okayama University Scientific Achievement Repository

MEMOIRS OF THE SCHOOL OF ENGINEERING, OKAYAMA UNIVERSITY, Vo!.l, No.1, MARCH, 1966Two Distinct Types of Spherulite in Poly (ethylene oxide)Yuhiko YAMASHITA, Fumiyoshi YOKOYAMA* and Kazuo MONOBEDepartment of Industrial Chemistry(Received November 20, 1965)Fujiwara's oriented crystallization method was applied to poly (ethylene oxide)to obtain a uniform texture composed of parallel fibrils which correspond to thestructure of a radial direction of spherulites. Two different x-ray diffractionpatterns in crystallite orientation of the spherulite radius were obtained. Fromthese patterns and crystallization conditions it could be determined that thespherulite radius has a [401 J rotation axis below about 50°C and two [421 Jand [421J rotation axes above about 50°C.A reasonable interpretation was given for these two ways of spherulitic cr) stal-lization, based on the growth features of lamellar crystals of poly (ethyleneoxide). That is, it is concluded that a second order transition in poly (ethyleneoxide) lamellar crystals near the temperature of 50°C is responsible for thechange of the rotation axis in spherulite radius.We wish to report that two distinct types ofspherulite are formed at different supercoolingsfrom the melt in poly (ethylene oxide) (PEG)and to give this fact a reasonable interpretation.Price and Kilb reported two distinct types ofPEG spherulite in Carbowax 4000 and Carbowax6000 for the first time!). They have indicatedthat at low supercoolings spherulites developscalloped edges, with each scallop sector havingbranched structure reminiscent of a fern frond,and at high supercoolings they develop smoothcircular boundaries. A x-ray diffraction studywas also made the capillary samples of spheru-lites and the crystallite orientation with respectto the spherulite radius was examined. Theyhave cnncluded that [401J rotation axis is ::tASoto the radius at low supercoolings and is per-pendicular to the radius at high supercoolings.This conclusion that the polymer chains aregenerally not in the tangential orientation, in--------- -------~* Present address: Okayama Industrial Research In-stitute, Ifuku, Okayama, Japan** In this method isothermal crystallization can berealized by moving a specimen rod, which is enclosedin a glass capillary, with a constant speed along a steeptemperature slope since most polymer spherulites havenegative values of temperature dependence of radialgrowth rate. Thus, the whole specimen rod comes topossess a uniform texture composed of parallel fibrilswhich correspond to the structure of a radial direction ofspherulite~.terests us in contrast with evolving concept ofmolecular orientation in polymer spherulites2).To examine their results, Fujiwara's orientedcrystallization method**3)4) was applied to PEG.By this method, oriented rods of PEG, Carbo-wax 6000, about 1 mm. in diameter, were pro-duced for various values of moving speed rang-ing from 0.008mm./min. to Imm./min. Thecrystallization temperatures in these conditionsare estimated to be approximately from 54°C to4SoC based on the data of the radial growthrate of Carbowax 6000 which were measured byPrice et a]5). Two different x-ray diffractionpatterns in crystallite orientation were obtainedfrom these specimens as shown in Fig. 1 (a) and(b). All reflections of them can be identified andindexed as from the monoclinic crystal structureproposed for PEG by Tadokoro et aI6). Fromthese patterns and crystallization conditions itcan be determined that the spherulite radiushas a [401J rotation axis below about 50°C andtwo [421J and [421J rotation axes above about50°C. In both cases the fact that these rotationaxes are perpendicular to the c axis makes chainmolecules the same tangential orientation asthat in other polymer spherulites. The transitiontemperature of the rotation axis is consistentwith that of morphologically different spheru-lites suggested by Price and Kilb!). However,our results on the crystallite orientation for th~60 Y. YAMASHITA, F. YOKOYAMA and K. MONOBE (Vol. 1,(a) (b)Fig. 1. X-ray diffraction patterns of spherulites prepared by oriented crystallization method.(a) Pattern obtained from the specimen crystallized below 50°C. Oriented rod axis vertical. Thespherulits radius has a [401J rotation axis.(b) Pattern obtained from the specimen crystallized above 50°C. Oriented rod axis vertical. Thespherulite radius has t\\"o [42Il and [421J rotation axes.radius are apparently inconsistent with thoseof them. These discrepancies seem to be due tothe following situations. In their capillary sam-ples formed at high supercoolings. a transcrys-talline layer seems to be produced for the reasonthat the whole capillary was cooled at a time.That is, spherulite nuclei at glass surface areso closely spaced that the spherulites grow inperpendicular direction to the capillary. In thespherulites formed at low supercoolings abovementioned discrepancy can not be understood,for it is likely that in their capillary samples aswell as ours the spherulite radius is parallel tothe capillary since the nuc:eation rate is verylow at these temperatures. It, however, shouldbe noticed that in our determination the [401Jaxis is not rotation axis but is oriented to ±4Sofor the radius.Lastly, we will give an interpretation for twodistinct spherulitic crystallization, based on thegrowth features of lamellar crystals of PEO. Ithas already been shown by many investigators7)8)9)10) that PEO is crystallized from dilutesolution in the form of square tabular crystalsthickening by way of screw dislocation me-chanism. In our previous paper8) it has beendetermined that the four growing faces are{120} of monoclinic cell and two diagonals arethe [401J and [010J axes, respectively. Here.it should be noticed that two axes of the [401Jand [010J are different in notation but very~i!TIilar in nature since sin~le crystals are squarein shape and their electron diffraction patternshave an approximately tetragonal symmetry.From more concentrated solution a dendriticdevelopment of lamellar crystals whose mor-phological habits are intermediate betweensingle crystals and spherulites was obtained.These crystals have a pronounced tendency forrapid growth to the diagonals as shown in Fig. 2.The extension of this marked habit for spheru-litic crystallization from the melt seem to givea simple interpretation for two distinct types ofspherulite as shown schematically in Fig. 3 ifit is assumed that at low supercoolings two axesof the [401J and [010J possess the similar ten-dency** for rapid growth and at high supercool-ings only a [401J axis possesses the tendencyfor rapid growth. This assumption seems to bereasonable from following facts. It can be point-ed out that the temperature at which two axesof the [401J and [010J possess similar habitcorresponds to that of beginning of sliding diffu-sion II) of chain molecules in crystals. The vis-coelastic absorption lYe characteristic of crystal-line regions in polymers such as polyethyleneis also attributed to the sliding diffusion l3l . Thepeak of the lYe absorption for solution growncrystals of PEO is located near the temperatureof SOoO·I). Furthermore, we have previously8)** The change of crystal structure above 50°C frommonoclinic to tetragonal was ruled out by photograph-ing x-ray diffraction patterns of fiber samples of PEOat a constant temperature of 5SoCI2l,1966) Two Distinct Types of Spherulite in Poly (ethylene oxide) fil(;. . )jt '.,\.//0/. U_:~ p/.1~p- .J .•Fig. 2. Electron micrograph of dendritic crystals crystallized from SGlution. These crystals havea pronounced tendency for rapid growth to the diagonals. This growth mechanism is due tothe way of screw dislocation. >~ 10,000(40 \) [42 I] 0'( [42 \1(120)~(421)~-I ~r~~ :r;;: NINI0 0'---'( I 20)(a)( I[40 I] Rota.tion Ax is(b)[4211or [4211 Rotdt ion Ax is(c)Fig. 3. A simple interpretation for two distinct types of spherulite in PEO is shown schematically.(a) Diagram which schematically represents growing planes and main crystallographic axes.(b) Since at high supercooling only a [401J axi::; possesses the tendeney for rapid growth,spherulite radius has a [401J rotation axis.(e) Since at low supercoolings two axes of the [401J and [OlOJ possess the tendency for therapid growth, spherulite radius has [421J and [421] rotation axes. One should notice thatin these crystals [401J and [010~ axes are not rotation axis as shown in x·ra>· diffractionpattern of Fig. 1 (b).62 Y. YAMASHITA, F. YOKOYAMA and K. MONoBEpointed out that the radial growth rate ofspherulites also changes abruptly at about 51°C.Therefore, it is not questionable that near thetemperature of about 50°C lamellar crystals ofPEO have a second order transition point andthis transition in crystalline regions is respon-sible for the change of rotation axis in spheru-lite radius.AcknowledgmentsThe authors would like to thank the late Prof.Nishio Hirai of the faculty of Science, OkayamaUniversity, for informative discussions, and toMr. Shoji Hirai for translating our mentalimages into drawings.References1) F. P. Price and R. \Y. Kilb: j. Polymer Sci., 57,(1962) 395.2) A. Keller: j. Polymer Sci., 17, (1955) 351.3) K. Tanaka, T. Seto and Y. Fujiwara: Rep. Prog.Polymer Phys. japan, 6, (1963) 285.4) Y. Fujiwara: j. Polymer Sci., 81, (1963) 675.5) W.]. Barnes, W. G. Luetzel and F. P. Pri2e: ].Phys. Chem., 65, (1961) 1742.6) H. Tadokoro, Y. Chatani, T. Yoshihara, S. Taharaand S. Murahashi: Makromol. Chem., 73, (1964)285.7) K. Kobayashi, H. Ota and S. Kumadani: Annu.Meeting Soc. Polymer Sci. (japan), Nagoya,May 1952.8) N. Hirai, Y. Yamashita and F. Yokoyama: KobunshiKagaku, 21, (1954) 724.9) W.]. Barnes and F. P. Price: Polymer, 5. (1954)283.10) F.]. Balta and A. Keller: J. Polymer Sci .. 2A,(1964) 2171.11) N. Hirai, T. Mitsuhata and Y, Yamashita: KobunshiKagaku, 18, (1951) 33.12) Y. Yamashita, M. Haisa and K. Monobe: to be pub-lished13) M. Takayanagi, T. Aramaki, M. Yoshino and K.Hoashi: j. Polymer Sci .. 46. (1960) 531.14) T. :\1inami: personal communication.

Two Distinct Types of Spherulite in Poly (ethylene oxide)

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