Showing papers in "Journal of Polymer Science Part A in 1976"

Liquid crystal polymers. I. Preparation and properties of p-hydroxybenzoic acid copolyesters†

Abstract: High molecular weight copolyesters were prepared by the acidolysis of poly(ethylene terephthalate) with p-acetoxybenzoic acid and polycondensation through the acetate and carboxyl groups. The mechanical properties of the injection-molded copolyesters containing 40–90 mole-% p-hydroxybenzoic acid (PHB) were highly anisotropic and dependent upon the PHB content, polyester molecular weight, injection-molding temperature, and specimen thickness. As the injection-molding temperature increased and the specimen thickness decreased, the tensile strength, stiffness, and Izod impact strength increased when measured along the direction of flow of the polymer melt, and the coefficient of thermal expansion was zero. In some compositions these properties were superior to those of commercial glass fiber reinforced polyesters. Maximum tensile strengths, flexural moduli, notched Izod impact strengths, and minimum melt viscosities were obtained with polyesters containing 60–70 mole-% PHB. Higher oxygen indicies (39–40) and heat deflection temperatures (150–220°C) were obtained with 80–90 mole-% PHB.

Poly(vinyl alcohol) hydrogels: reinforcement of radiation-crosslinked networks by crystallization.

Abstract: Aqueous poly(vinyl alcohol) solutions were crosslinked via electron-beam irradiation to form transparent hydrogels of varying crosslinking densities. Typical crosslinked hydrogels with anti M/sub c/ between 3500 and 8000 were weak, easily shattered, nonextensible materials with very low tensile moduli (up to 70 psi) and tensile strengths at break (less than 10 psi). Reinforcement by induction of partial crystallization was accomplished by a two-stage drying process, consisting of a slow dehydration stage at room temperature and an annealing stage at elevated temperatures, which was mainly responsible for the introduction of the crystallites. The swollen hydrogels after the annealing process had crystallinities widely varying between 30 and 65 percent and polymer volume fractions between 30 and 60 percent, depending on the temperature--time history of the specimen. These materials showed greatly improved mechanical properties (modulus, ultimate tensile strength, tear strength), as compared to the uncrystallized hydrogels.

High‐conversion polymerization. I. Theory and application to methyl methacrylate

Abstract: The concept of polymer entanglements has been applied in conjunction with classical free-radical kinetics to describe vinyl polymerizations carried to high conversion A kinetic model has been developed on the assumption that two populations of radicals exist in a high-conversion polymerization system: those radicals whose chain lengths are long enough to become entangled with neighboring molecules and have, therefore, a restricted mobility; and those shorter radicals whose mobilities are not strongly affected by diffusional effects It has also been assumed that the kinetic rate constant for the termination step between entangled radicals is inversely proportional to the mean entanglement density The model contains only two parameters in addition to the kinetic rate constants required to describe low-conversion polymerizations One of these parameters can be determined, at least in principle, from measurements of solution properties of the polymer-monomer mixtures The model so developed has been tested against experimental data obtained from the literature on the bulk polymerization of methyl methacrylate The agreement between predicted and experimental monomer conversions and molecular weight averages is found to be satisfactory

Synthesis and structure of the p-hydroxybenzoic acid polymer

Abstract: The synthesis and structure of the p-hydroxybenzoic acid polymer is described. The polymer was successfully prepared from either the phenyl ester of p-hydroxybenzoic acid or from p-acetoxybenzoic acid. With highly purified acetoxybenzoic acid, single crystals of the polymer could be prepared. The structure of the polymer was determined and shown to consist of a double helix where the two chains are in a reversed head-to-tail order. The unit cell dimensions are: a = 17.8 A and c = 18.4 A, where c corresponds to the chain length with a repeat distance of three units. The mechanism of polymerization and formation of the single crystal is discussed. The polymer displays a reversible high-temperature crystalline transition at 325–360°C (not a melting point). The transition was characterized by differential thermal analysis, differential calorimetry, thermal expansion coefficient measurements, high-temperature x-ray scans, and dielectric constant determinations. Orientation of the polymer chains during fabrication and changes in the mechanism of oxidative degradation above the crystal transition are described.

Polyimide structure-property relationships. II - Polymers from isomeric diamines

Abstract: An extensive study of the effects of stereoisomeric variations in aromatic polyimide structures on polyimide properties was conducted. The structural variations were incorporated into the polyimides through the use of two complete series of isomeric aromatic diamine monomers, the diaminodiphenylmethanes and the diaminobenzophenones, as well as several pairs of diamine isomers. The ability of the diamines to polymerize was related to the basicities, and thus reactivities, of the amino groups. Diamines with an amino group located ortho to the group connecting the two aromatic rings were successfully polymerized with dianhydrides for the first time to high molecular weight poly(amic acids). The stereoisomeric polyimides were characterized by determining the glass transition temperatures Tg, mechanical properties, and thermooxidative stabilities of thin films of the polymers. The polymers prepared from p-diamines were shown to have the highest softening points and thus, the most rigid molecular structures. Those synthesized from m-diamines had the lowest Tg values, inferring the most flexible molecular backbone. With limited exceptions, the use of diamines with ortho-oriented amine groups failed to improve the flexibility of the polyimides since their Tg values were usually as high as those of polymers made from p-diamines. Only slight differences in mechanical properties of the isomeric polyimide films were attributable to the variations in isomeric structure, except for those properties dependent upon Tg changes, such as elevated temperature mechanical properties. A study of the thermooxidative stability of the polyimides showed little difference between the polymers prepared from the diaminobenzophenones, but marked differences were observed between the individual members of the diaminodiphenylmethane-derived polyimides.

Emulsifier‐free emulsion polymerization with cationic comonomer

Abstract: An earlier article1 described the emulsion polymerization of styrene and various anionic comonomers, together with an anionic initiator, to give uniform latices at ca. 35% solids content. This article extends the work to cationic systems. Cationic comonomers 1,2-dimethyl 5-vinylpyridinium methylsulfate and 1-ethyl 2-methyl 5-vinylpyridinium bromide were synthesized and used with azobis(isobutyramidine hydrocholoride) initiator in the emulsifier- free emulsion polymerization of styrene. Recipes and results were generally comparable to those of the anionic systems, excepts for the dependence of particle diameter on comonomers concentration. Here the initial decrease was followed by an increase in particle diameter at higher comonomer content. The surface charge increased sharply with comonomer content.

Plasma polymerization of some organic compounds and properties of the polymers

Abstract: Plasma polymerizations (under 13.5-MHz radiofrequency inductively coupled glow discharge) of some organic compounds are investigated by their properties (elemental analysis, surface energy, and infrared spectra) and their relations to the concentrations of free radicals in the polymers as detected by electron spin resonance (ESR) spectroscopy. Monomers that have been investigated are hexamethyldisiloxane, tetrafluoroethylene, acetylene, acetylene/N2, acetylene/H2O, acetylene/N2/H2O, allene, allene/N2, allene/H2O, allene/N2/H2O, ethylene, ethylene/N2, ethylene oxide, propylamine, allylamine, propionitrile, and acrylonitrile. Plasma-polymerized polymers generally contain oxygen, even if the starting monomers do not contain oxygen. This oxygen incorporation is related to the free-radical concentration in the polymer. Molecular nitrogen copolymerizes with other organic monomers such as acetylene, allene, and ethylene, and their properties are very similar to those of plasma-polymerized polymers from nitrogen-containing compounds such as amines and nitriles. The addition of water to the monomer mixture reduces in a dramatic manner the concentration of free radicals in the polymer and consequently the oxygen-incorporation after the polymer is exposed to air. The concentrations of free radicals (by ESR) are directly correlated to the change of the properties of plasma-polymerized polymers with time of exposure to the atmosphere. These changes are primarily the introduction of carbonyl (and possibly hydroxyl) groups. The addition of water to the plasma introduces these groups during the polymerization.

Applications of ESCA to polymer chemistry. XI. Core and valence energy levels of a series of polymethacrylates

Abstract: The core and valence levels of a series of poly(alkyl acrylates) have been studied by ESCA. From an analysis of the individual component peaks for the C1s and O1s core levels and from comparison of relative area ratios it is shown that ESCA may be applied to the study of surface compositions. The evidence presented strongly suggests that on the ESCA depth-profiling scale the technique statistically sample the repeat units with no evidence for preferential orientation of side chains at the surface. For some samples, ESCA provides evidence for a degree of surface oxidation and hydrocarbon contamination. The valence energy levels are shown to be characteristic of the polymer system. The measured absolute and relative binding energies of the core levels have been compared with model calculations using the charge-potential model in the CNDO/2 SCF MO formalism.

Application of ESCA to polymer chemistry. VIII. Surface structures of AB block copolymers of polydimethylsiloxane and polystyrene

Abstract: The surface morphology of a number of films of AB block copolymers of polydimethylsiloxane and polystyrene was examined by ESCA and contact angle measurements. In all cases the immediate surface is shown to consist of an essentially pure polydimethylsiloxane component. By comparing the intensities of elastic peaks corresponding to photoionizations from core levels without energy loss for polydimethylsiloxane and polystyrene with those for the block copolymers and by consideration of shake-up phenomena specific to the polystyrene component, an estimate of the thickness of the polydimethylsiloxane outer layer of the latter may be obtained. This is shown to vary between ∼13 and 40 A, depending on the method of formation of copolymer film.

Spatially intermittent polymerization

Abstract: A novel reactor has been designed which permits the precise determination of absolute rate constants in photoinitiated free-radical vinyl polymerization. A solution of monomer and initiator flows through a dark tubular reactor past regularly spaced slots through which light shines. The alternating dark and light regions produce spatially intermittent polymerization (SIP) and make the system analogous to the well-known rotating-sector technique. However, the SIP reactor has the advantage of producing large volumes of reaction product, at low conversion, suitable for analysis of both conversion and molecular weight. This supplies the necessary data, from a single set of experiments, for the simultaneous determination of the rate constants for propagation and termination. Experimental data are reported at 25°C for methyl methacrylate which indicate that kp = 315 I./mole-sec, independent of polymer molecular weight, and kt is dependent on molecular weight especially at low molecular weight, approaching a lower value of kt = 30 × 106 I./mole-sec at a molecular weight of 106. For styrene, measurements being made only at high molecular weight, kp = 74 ± 5 and kt = 37 ± 0.3 × 106 l./mole-sec at 25°C.

Effect of evolved hydrogen fluoride on radiation‐induced crosslinking and dehydrofluorination of poly(vinylidene fluoride)

Abstract: Poly(vinylidene fluoride) (PVdF) was irradiated by 60Co γ-rays with and without potassium hydroxide (KOH) under vacum. KOH tablets were added to absorb completely hydrogen fluoride (HF) which is the main volatile product of radiolysis of PVdF in the irradiation cell. In the presence of HF, the rates of radiation-induced crosslinking and dehydrofluorination of PVdF were lower than those in the absence of HF. The experimental results are discussed from the standpoint of stabilization of alkyl free radicals in PVdF by reaction with hydrogen fluoride.

Oxysilane polymers from silanediol–bisdimethylaminosilane polycondensations: Synthesis and properties

Abstract: The solution polycondensation of 1,4-bis(hydroxydimethylsilyl)benzene with six bis(dimethylaminosilanes) was carried out by the aminosilane deficient method to give a series of high polymers. The bis(dimethylaminosilanes) were bis(dimethylamino)dimethylsilane, bis(dimethylamino)methylphenylsilane, bis(dimethylamino)diphenylsilane, 1,4-bis(dimethylaminodimethylsilyl)benzene, 1,3-bis(dimethylamino)-1,1,3,3-tetramethyldisiloxane, and 1,5-bis(dimethylamino-1,1,3,3,5,5-hexamethyltrisiloxane). The condensation of dihydroxymethylphenylsilane with bis-(dimethylamino)methylphenylsilane to give polymethylphenylsiloxane was also performed. A detailed description of the monomer syntheses and polymerization reactions is provided, since this paper represents the first detailed and systematic description of this polycondensation as an alternative to disilanol or disilanol-dichlorosilane condensation routes. The thermal properties (i.e., Tg, TGA, DSC) of poly(p-phenylenetetramethylsiloxane) are compared to those of poly[1,4-bis(oxydimethylsilyl)benzenel] (where a Si(Me)2O group has been inserted between the silylphenylene units) as well as others in this series, polydimethylsiloxane, and polymethylphenylsiloxane. Similarly, these properties are compared with those of related polymers which include in-chain ferrocene units. Introduction of Si(Me)2O units into poly(tetramethyl-p-silylphenylenesiloxane) systematically decreases Tg and thermal stability. Replacing SiCH3 with SiC6H5 groups increases Tg and thermal stability. Replacing in-chain C6H4 with ferrocene increases Tg and slightly decreases thermal stability. The values of K and A in the Mark-Houwink equation were determined for several polymers.

Formation of free radicals in photoirradiated cellulose. VIII. Mechanisms

Abstract: Photoinduced free radicals in cellulose were studies by means of ESR spectroscopy. Plausible mechanisms have been suggested for each type of intermediate radical to account for the ESR spectra observed and for the product balances. Based on the principles of photochemistry of cellulose, coupled with the findings of the ESR spectra, it becomes evident that localization of the energy absorbed in the cellulose molecule leads to formation of free radicals in terms of chain scission, dehydrogenation, dehydroxylation, and dehydroxymethylation. Emphasis has been placed on the correlation of the mechanisms of photodegradation and the mechanisms of photoinduced graft copolymerization.

Active polycondensation of diethyl 2,3,4,5‐tetrahydroxyadipate with diamines

Abstract: Polycondensation of diethyl 2,3,4,5-tetrahydroxyadipate with various diamines was carried out in solutions under mild conditions. The polycondensation reaction occurred rapidly even at room temperature in polar solvents such as alcohols, and in aqueous solution a cyclic product was obtained instead of linear polymers although the reaction with diamines was completed within several minutes. Polymers obtained from diethyl 2,3,4,5-tetrahydroxyadipate were a linear polyamide having pendant hydroxyl groups, which decomposed on heating at around 200°C. A solid-phase polycondensation of the precursor polyamide yielded a high molecular weight polyamide.

ESCA studies of polymers. VII. Shake‐up phenomena in some alkane–styrene copolymers

Abstract: Shake-up satellites corresponding to π* π transitions accompanying C1s core ionizations have been studied for polystyrene and a series of alkane–styrene copolymers. It is shown that the shake-up intensities are additive in nature and give a direct measure of copolymer compositions.

Free‐radical polymerization of vinylferrocene. II. Spectroscopic and physical properties

Abstract: The spectroscopic and physical properties of poly(vinylferrocene) prepared by free-radical polymerization in benzene are discussed. The results obtained in these studies are in accord with the kinetic analysis of the polymerization reactions in benzene. ESR spectroscopy shows that the polymer is paramagnetic and contains a species which is identified by Mossbauer spectroscopy as an ionically bound complex of Fe(III) in a high spin (3d5) configuration. The concentration of this species is shown to be dependent upon kinetic parameters. Magnetic susceptibility measurements show that the polymer does not contain any oxidized ferromagnetic impurities. Infrared spectroscopy indicates that the polymer contains vinylidene groups. The presence of these groups is explained by chain transfer to monomer followed by reinitiation. Ultraviolet spectroscopy also suggests the presence of unsaturation in the polymer. Gel-permeation chromatography indicates that poly(vinylferrocene) is branched even at low conversions. The effect of transfer reactions and the intramolecular electron transfer termination of the chain radical on the structure of poly(vinylferrocene) is discussed. The glass transition temperature and thermal stability of the polymer are also examined.

Supported catalysts for stereospecific polymerization of propylene

Abstract: Tetrabenzyltitanium (B4Ti), tribenzyltitanium chloride (B3TiCl), tetra(p-methylbenzyl)titanium (R4Ti) and tri(p-methylbenzyl)titanium chloride (R3TiCl) have been used as catalysts for ethylene and propylene polymerization activated by AlEt2Cl. B4Ti-AIEt2Cl in solution polymerizes ethylene readily but its activity decays rapidly. B4Ti was also supported on Cab-O-Sil, Alon C, and Mg(OH)Cl. The last support was found to give catalyst with longest lifetime with a rate of polymerization, Rp = 7.0 g/hr-mmole Ti-atm ethylene. 14CO counting techniques gave 1.13 × 10−3 mole of propagating center per mole of B4Ti; the rate constant of propagation, kp = 540 l./mole-sec. None of the tetravalent titanium compounds polymerize propylene in solution. However, when supported on Mg(OH)Cl, Cab-O-Sil, Alon C, Cab-O-Ti, and charcoal, they all polymerize propylene. In this work the supports were characterized by various techniques, including the paramagnetic probe method, to determine the concentration and nature of surface hydroxyls. Those factors controlling the rate and stereospecificity of propylene polymerization were investigated. The system B3TiCl–Mg(OH)Cl–AlEt2Cl is the most active with Rp = 2.89 g/hr-mmole Ti-atm propylene. The concentration of propagation center is 0.9 × 10−3 mole per mole of B3TiCl; kp = 32 l./mole-sec. This catalyst gave only about 70% stereoregular polymer. Diethyl ether is found to raise stereospecificity to 100%, but there is a concommittent tenfold decrease of activity. Other interesting catalyst systems are: (π-C5H5)TiMe3–Mg(OH)Cl–AlEt2Cl (1.56, 89.5); (π-C5H5)TiMe2–Mg(OH)Cl–AlEt2Cl (0.075, 94.5); and (π-C5H5)TiMe3–Alon C–Al-Et2Cl (0.08,97.2), where the first number in the parenthesis is Rp in g/mmole Ti-hr-atm and the second entry corresponds to percentage yield of stereoregular polypropylene. Hafnocene and titanocene supported on Mg(OH)Cl produce only oligomers of propylene.

Polymerization of hexamethylcyclotrisiloxane with a biscatecholsiliconate. I. Nature of polymerization

Abstract: Polymerization behavior of hexamethylcyclotrisiloxane (D3) in toluene solution with the use of benzyltrimethylammonium bis(o-p;henylenedioxy)phenylsiliconate as a catalyst, dimethyl sulfoxide as promoter, and adventitious moisture as initiator was investigated. The polymerization system gives a linear difunctional polymer, HO(Me2SiO)xH, with a molecular weight which is inversely proportional to the amount of water reacted rather than to the amount of catalyst employed. The polymerization in the presence of H2O gives rise to molecular weight distributions very close to Poisson distributions. The normalized experimental GPC curve agrees very well with the theoretical GPC curve calculated from the polymerization scheme: Polymerization carried out in the combined presence of H2O and ROH, where R is Me or Me3Si, gives rise to bimodal molecular weight distributions. The resulting polymers consist of HO(Me2SiO)2xH and RO(Me2SiO)xH. The molecular weight of the former is twice that of the latter, and their proportion depends on the ratio of H2O to ROH. The system is a special type of “living” polymer.

Voltammetric behavior of poly(vinylferrocene)

Abstract: A voltammetric analysis of the electron-transfer process in poly(vinylferrocene) (PVF) has been carried out; the results indicate that the electrochemical behavior of ferrocene and PVF are quite similar. The field effects in the macromolecular environment do, however, appear to influence the microscopic potential for oxidation of adjacent ferrocene residues in PVF. Analysis of the slopes of plots of limiting current versus the square root of the rotation speed indicate that only “isolated” ferrocene residues in the polymers are oxidized under the conditions of the rotating-disk electrode experiment. Diffusion coefficients were determined experimentally for ferrocene and its macromolecular analogs were quite close to those simply calculated from the Stokes-Einstein relationship. Further, it was demonstrated that the molecular weight, which is inversely proportional to the diffusion coefficient, could be determined by voltammetric techniques.

Synthesis of monomers that expand on polymerization. Synthesis and polymerization of 3,9‐dimethylene‐1,5,7,11‐tetraoxaspiro[5.5]undecane

Abstract: A spiro ortho-carbonate containing two double bonds, 3,9-dimethylene-1,5,7,11-tetraoxaspiro[5.5]undecane (III) was prepared from 2-methylene-1,3-propanediol (VI). The structure of the monomer was indicated by its elementary analysis as well as its infrared and NMR spectra. When the crystalline monomer was polymerized with Lewis acids such as trifluoride etherate as catalysts, soluble polymer with a high molecular weight was obtained. The infrared and NMR spectra indicated that the polymer was an alternating copolymer of ether and carbonate having double bonds. When the usual monomers such as vinyl chloride and styrene polymerize, shrinkage occurs. However, this monomer underwent expansion on polymerization.

Amide‐exchange reactions in mixtures of N‐alkyl amides and in polyamide melt blends

Abstract: The amide-exchange reactions which cause copolymer formation in polyamide melt blends were studied with mixtures of N-ethylcaproamide and N-hexylacetamide containing small concentrations of caproic acid and hexylamine as a model system for melt blends of aliphatic polyamides. Amide exchange was found to involve acidolysis and aminolysis reactions with no detectable contribution of direct reaction between amide groups. Kinetics data are consistent with formation of an anhydride intermediate in amide acidolysis. Rate constants over the range 200–275°C and activation energies for amide acidolysis and aminolysis reactions are given. Equations are given for calculating amide exchange rates in polyamide melt blends and for relating degree of amide exchange to block copolymer composition.

Thermal degradation of poly(bismaleimides)

Abstract: Thermal decomposition of poly(bismaleimides) has been investigated by using programmed and isothermal thermogravimetric analysis (TGA) in nitrogen. Reaction rates and overall activation energies were calculated from isothermal weight less studies. For five aliphatic poly(bismaleimides) a linear correlation between the activation energies and the number of methylene groups in the sequence between the maleimide residues was found. Aliphatic poly(bismaleimides) follow first-order kinetic law up to a conversion of 60-70% having activation energies between 196 and 256 kj/mole. poly(2,4-bismaleimidotoluene) which was found to have in highest polymer decomposition temperature (PDT) did follow the first-order kinetics up to a conversion of 60% in contrast to other aromatic poly(bismaleimides). In addition to the TGA, the pyro-field ion mass spectra of the polymers were recorded and are discussed.

Determination of molecular weight distribution of cellulose by conversion into tricarbanilate and fractionation

Abstract: Two samples of cellulose (molecular weight 2.97 × 105 and 1.25 × 105) were transformed into carbanilates (CTC) which were then fractionated by the elution method at a constant composition of the acetone-water elution mixture with the column temperature gradually increasing from −30°C to 30°C, and by the GPC method in acetone and tetrahydrofuran. Tetrahydrofuran appeared to be a more suitable solvent. The molecular weights of fractions obtained by the elution fractionation were determined by the light-scattering method in tetrahydrofuran. The width of fractions was determined by the GPC method (average Mw/Mn = 1.37); the [η] values and the Mark-Houwink constants (K = 5.3 × 10-3, a = 0.84) for tetrahydrofuran at 25°C were determined. The calibration curve for the GP method was constructed by means of the fractions thus obtained; it was demonstrated that the universal calibration curve according to Benoit can also be used. It was demonstrated that the molecular weight distribution of cellulose can be conveniently determined by conversion into CTC followed either by the elution fractionation (for preparative purposes) or by fractionation by the GPC method (for analytical purposes).

Reactivity changes during polyimide formation

Abstract: The raactivity changes which occur in diamine monomers during polymide formation were investigated. A series of aromatic diamines were reacted with three aromatic anhydrides (including 1,4,5,8-naphthalene tetracarboxylic dianhydride) under different conditions and the products isolated and identified. There was a great range of reactivity changes depending on the conjugation between the two amino groups of the diamine monomer. For highly conjugated groups, imide formation at one group can prevent any reaction at the other, and hence polymer formation is curtailed.

Para‐ordered polybenzimidazole

Abstract: A series of novel AB monomers such as 2-[p-carboxyphenyl]-5,6-diaminobenzimidazole hydrochloride have been synthesized. In addition, a new aromatic monomer, 1,3-diamino-4,6-bis(p-toluenesulfonamido)benzene has been prepared in high purity and substituted for 1,2,4,5-tetraaminobenzene in a polymerization with terephthalic acid. Homopolymerization of the AB monomers, and polycondensation of monomer with terephthalic acid in polyphosphoric acid, produced the rod-like para-oriented polymer, poly[1,7-dihydrobenzo(1,2-d: 4,5-d)diimidazole-2,6-diyl-1,4-phenylene]. The yellow polymer was completely soluble in methanesulfonic acid (MSA) and PPA, exhibiting intrinsic viscosities as high as 5 dl/g in MSA, and a blue opalescence in solution. Polymerization at temperatures above 225°C caused crystallization and subsequent precipitation to occur. Polymer thus obtained was completely insoluble in MSA and possessed a high degree of crystallinity as demonstrated by x-ray analysis.

Formation of free radicals in photoirradiated cellulose and related compounds

Abstract: Free-radical formation in various modifications of celluloses, namely, wood cellulose I, II, III, and IV, rayon cellulose, amorphous cellulose, cotton linters, and absorbent cotton, irradiated with ultraviolet light, has been studied by means of ESR spectroscopy at 77°K. Various types of free radicals were generated from these samples. The line shapes and the signal intensities of the ESR spectra depended greatly upon the degree of crystallinity, the lattice type, and the arrangement of molecules in cellulose. The effect of degree of crystallinity and the amount of sensitizer (Fe3+) absorbed revealed that photochemical reactions in cellulose occurred exclusively in the amorphous regions of the polymer. Free radicals formed in these samples behaved distinctively upon a warm-up process. Phenomena of radical migration and formation of new radicals were observed from the sensitized samples of rayon cellulose and amorphous cellulose.