Yurii Lipatov 

Yu.S.LIPATOV: LIFE AND PROFESSIONAL CAREER

 Tamara Todosiichuk, Taisa Ignatova, Valeriy Rosovitskiy 

(Translated by G.G. Lypskyi)

On 10 July 2022, we celebrate the 95th anniversary of Yu.S. Lipatov, a well-known scientist in the field of macromolecular science, a full Member of the National Academy of Sciences of Ukraine, a Member of the International Academy of Creative Endeavour. His scientific activity is connected with solving fundamental problems of physical and colloid chemistry of multicomponent polymeric systems. He is the author of more than 1300 scientific papers and 19 books (5 translated into English). Yuri Sergeevich Lipatov was born in the city of Ivanovo-Voznesensk. His father, Sergei Mikhailovich Lipatov, a graduate of Moscow University and thereafter an employee at the laboratory of the local textile plant, was then involved in the physicochemical studies of dyeing. Two years later academician N.A. Bakh, the director of the L.Ya. Karpov Institute of Physical Chemistry (KPCI) in Moscow, offered a research position to S.M. Lipatov in that Institute, and in 1929 he moved with his family to Moscow. The first lodging of the family in Moscow was a room in the Institute building; thus, KPCI was the first scientific cradle of Yu.S. Lipatov. In 1940, S.M. Lipatov was elected the Member and the  ice-President of the Academy of Sciences of Byelorussia and the family moved to Minsk, the Republic's capital city. The period from midsummer 1941 to 1943 the Lipatov family spent in Tashkent where S.M. Lipatov made many efforts reorganizing the activities of the Academy in the conditions of exile, and teaching at the chair of colloid chemistry in the Central-Asian State University. During this period, Yu.S. Lipatov studied qualitative chemical analysis and, at the same time, helped his father in measurements of polymer solutions viscosity.

In the summer of 1943, after the family returned to Moscow, Yu.S. Lipatov graduated from the secondary school by correspondence, and in winter of 1944 was admitted as a student of the Department of Technology at I.M. Gubkin Oil Institute, Moscow. While the 4th year student of this Institute, he attended the lecture course on polymer chemistry read by V.I. Isagulyantz, a Member of the Academy of Sciences of Armenia. The development of the physicochemical way of thinking of Yu.S. Lipatov was profoundly influenced by the comprehensive course of physical chemistry read by Prof. G.M. Panchenkov, as well as by regular discussions with his father over many years.

In 1947 Yu.S. Lipatov married his group-mate, Tatiana Esperovna Sosnina; under supervision of Prof. Ya.M. Paushkin, the newly-weds made a joint diploma work at the chair of organic chemistry headed by academician A.V. Topchiev.

Having graduated from the Institute with the diploma on “Oil and Gas Technology”, Yu.S. Lipatov was hired as an engineer of Technology Department at the Central Institute of Oils and Combustibles for Aviation, Ministry of Oil Industry, and worked there till 1951.

In 1951, Yu. S. Lipatov published his first scientific paper on catalytic cracking in the prestigious Reports of the Academy of Sciences of the USSR. By the end of this year, he started his post-graduate studies on “Orientation Phenomena in Crystalline and Amorphous Polymers” under the supervision of academician V.A. Kargin, head of the Laboratory of Colloid Chemistry in the KPCI, and of Prof. G.L. Slonimsky. During the same period, T.E. Lipatova (formerly Sosnina), was preparing her PhD thesis under the supervision of academician S.S. Medvedev, head of the Laboratory of Polymerization Processes in the KPCI. In 1954, the young Lipatovs couple were granted their two PhDs.

The main issue of Yu.S. Lipatov’s thesis was the invalidity of.the then accepted concept of orientation as promoting a “higher order and denser packing of macromolecules, as well as lower enthalpy. He managed to show that orientation led to a lower order and looser chain packing in amorphous polymers, while in the case of crystalline polymers, on the contrary, the packing density tended to increase. These changes were attributed to the kinetics-controlled processes of chain reorientations, which depended on the initial chain conformation, and the level of intermolecular interactions. The glass transition temperatures of amorphous polymers were found to decrease with orientation, which was explained by concomitant conformation entropy losses.

In 1955 Yu.S. Lipatov started the cooperation with the reference journal Chemistry as a reviewer and subsequently, as the Section Editor. This cooperation lasted till 1995; thousands of publications which were edited by Yu.S. Lipatov during this 40-year-long period proved indispensable as regards continuous updating of his knowledge of hot topics in different fields of contemporary polymer science.

During the period from the late 1954 to 1959, Yu.S. Lipatov worked as a senior researcher in the Laboratory of Colloid Chemistry at KPCI. Having accepted the position in the group of Prof. P.I. Zubov, the director of the KPCI, he launched the new research in the field of rheology of concentrated solutions of polyelectrolytes and of gelation effects on heating. The results of this research were published in Russian journals Colloid Journal, Polymer Science, Advances in Chemistry and formed the basis of his DSc thesis.

    It was established that redistribution of the number of interand intramolecular bonds accompanying the increase of solution concentration and concomitant conformational changes led to drastic changes in solution properties. This was attributed primarily to 1971 formation of the spatial network of macromolecular aggregates spanning the entire solution volume and responsible for the onset of gelation phenomenon.

Shear-induced chain stretching and concomitant increase of the level of interchain interactions were assumed as the main structural changes in concentrated polyelectrolyte solutions. The extensive studies of rheology and thermodynamics of such solutions were the basis of new concepts of the onset of gelation at limiting polymer concentration both on heating and on cooling. These concepts were further developed by Yu.S. Lipatov in his theory of the aggregative adsorption of polymers from solutions.

Hard living conditions in Moscow forced Yu.S. Lipatov to look for a position in other research centers. In the late 1959 T.E. Lipatova and himself were granted the positions of senior researchers at the Institute of General and Inorganic Chemistry (IGIC), Academy of Sciences of Byelorussia, and moved to Minsk where they co-organized the Laboratory of Reinforced Plastics. As recommended by V.A. Kargin, the research in this laboratory was focused on two main issues: physical chemistry of reinforcement, and new routes of synthesis of polymeric binders. The expertise gained by T.E. Lipatova and Yu.S. Lipatov in the laboratories of S.S. Medvedev and V.A. Kargin in the KPCI proved indispensabie in solving new problems, which faced their laboratory. In several issues of Polymer Sciences, (1960), Yu.S. Lipatov published his first papers on polymer —filler interactions, which can be now regarded as the milestones of his life-long favourite research area. During the same period, the first studies of polymer grafting onto solids treated with polymerization catalysts were jointly published by T.E. Lipatova and Yu.S. Lipatov.

At the beginning of 1960, Yu.S. Lipatov was elected the head of the Laboratory of Reinforced Plastics, IGIC, and in May of this year he was promoted to the position of deputy director of research in that Institute. His research activities combined with teaching a polymer chemistry course at the Chemical Department of the State University of Byelorussia, and supervising PhD theses, had set the path for the development of polymer science in Byelorussia, in which many of his former students are still active.

In the early 1960’s V.A. Kargin proposed the Lipatovs to start joint research on the use of polymers in medicine. Unfortunately, the existing conditions in Byelorussia at those times were not favorable for this undertaking, and it had to

be put aside till 1966, when the Lipatovs were already working in the Institute of Macromolecular Chemistry (IMC), Academy of Sciences of Ukraine (Kyiv). Five years of physicochemical studies of filled polymers permitted Yu.S. Lipatov to lay down the foundations of this research area which became later on (beginning from 1981) the leading one in the IMC.

Having summarized the data obtained in the studies of concentrated polymer solutions and filled polymers, Yu.S. Lipatov had successfully defended the DSc thesis “Studies of the Structure Formation in Concentrated Polymer Solutions and in Filled Polymers” (KPCI, 1963, official opponents: academician P.A. Rhebinder and Profs. P.V. Kozlov and G.L. Slonimsky). The main conclusions of this thesis were the following. Redistribution of inter- and intramolecular bonds under the

influence of either solution concentration, or presence of the solid phase is the fundamental mechanism of structure formation in both concentrated polymer solutions and filled polymers. Secondary structures (i.e. macromolecular aggregates) are the main structure building blocks in both cases. The concept of interactions of secondary structures with the solid surface was used for the first time to explain the features by which the properties of boundary layers, such as packing density, glass transition temperatures, thermomechanical behaviour, etc., differ from those of the bulk polymer phase. These concepts were used to formulate practical recommendations on how to change conditions of preparation of a filled polymer to reach the desired physical chemical properties.

In 1964, Yu.S. Lipatov was given the rank of professor in physical chemistry. In the spring of 1964, V.A. Kargin, the Chairman of the Scientific Council on Macromolecular Compounds (SCMC) of the Academy of Sciences of the USSR summarized his inspection of research activities in different polymer centers all over the country and declared, that further research in the field of polymer science in the Republic of Byelorussia made no sense. Thus, to be able to continue his scientific career, Yu.S. Lipatov was forced again to look for a job in yet another center. Asked for an advice, V.A. Kargin did not react. Fortunately, academician N.M. Emanuel, who was then a highranking official in the Presidium of the Academy of Sciences of the USSR, in the summer of 1964 recommended the Presidium of the Academy of Sciences of Ukraine to consider Yu.S. Lipatov as a person capable of improving the reportedly unsatisfactory state of basic research in polymer science in the Republic of Ukraine. Yu.S. Lipatov was invited to Kyiv for an interview with academicians B.E. Paton, President, and V.S. Gutyrya, Vice-President of the Academy of Sciences of Ukraine and soon thereafter, in the autumn of 1964, he accepted the permanent position in the Institute of Macromolecular Chemistry. In March 1965, he was promoted to the position of the acting director of the IMC, and then he was Officially elected the director of the IMC at the general assembly of the Academy of Sciences of Ukraine.

Simultaneously, he became the head of the Department of Physical Chemistry of Polymers at the IMC. The immediate task that faced Yu.S. Lipatov as the directorelect was the reorientation of the IMC to the new research field of chemistry and physical chemistry of polyurethanes (PUs), as was recommended by the Academy of Sciences of the USSR. The implementation of this task into reality started after the meeting of the SCMC of the Academy of Sciences of the USSR, with V.A. Kargin as the chairperson, where Yu.S. Lipatov outlined the strategy of reorientation. The main research issues were the following:

·        elucidation of the reasons for special physical and physicochemical properties of PUs in relationship to their chemical composition and physical structure, with the aim of optimizing synthesis of cross-linked polymers;

·        synthesis of oligomers for preparation of PUs

·        mechanism and kinetics of migration polymerization and reactivity of monomers, mechanisms of catalysis and structure regulation of three-dimensional networks

·        principles of preparation of technically important end products on PU base (films, adhesives, coatings, etc.).

   This program was approved by the Presidium of the Academy of Sciences of Ukraine on May 4, 1965. The second half of 60’s was the period of establishment of new research directions in the field of PUs, as weil as restructuring of the IMC, including creation of new laboratories and the experimental pilot plant; the latter was oriented towards adaptation of the basic research data to industry. These timeconsuming organization efforts of Yu.S. Lipatov were combined with the further development of personal fields of interest, such as physicochemical research of PUs and filled polymers, including pioneering studies of filied PUs.

   The first book of Yu.S. Physical Chemistry of Filled Polymers (Naukova Dumka, Kyiv, 1967), proved to be the first ever book on this subject worldwide. This book summarized and generalized the currently available knowledge on the basic physicochemical properties of filled polymeric materials; special emphasis was laid on the features of interfacial interactions at the polymer — filler boundary, on new insights into adhesion, adsorption and relaxation phenomena, on filler effect on phase and physical structures of polymers, and on the mechanism of filler reinforcement.

All these aspects obtained further development over the years by Yu.S. Lipatov and by his former students and staffers (Yu. Yu. Kercha, E.V. Lebedev, L.M. Sergeeva, V.P. Privalko, V.V. Shilov, F.G. Fabulyak and others).

In 1967, V.A. Kargin repeated his request to start the research in the field of polymers for medicine. This time the situation proved much more favourable, and Yu.S. Lipatov spent much efforts to create the appropriate experimental facilities in the IMC. Shortly after the start of this project he managed to set up the unique complex which included sections of chemistry, physical chemistry, biochemistry, histology, surgery, as well as the vivarium; the basic research was aimed at the development of biocompatible polymers. On recommendation of V.A. Kargin, T.E. Lipatova was nominated the head of this new complex; however, over many years Yu.S. Lipatov took an active part in this research field as witnessed by numerous joint publications.

In 1970, Yu.S. Lipatov (in collaboration with Yu. Yu. Kercha and L.M. Sergeeva) published the first book on PUs in them USSR entitled Structure and Properties of Polyurethanes (Naukova Dumka, Kyiv). This book turned out also to be unique worldwide, in so far as it covered such aspects as thermodynamic properties of PU solutions; the impact of the nature of chemical and physical bonding on the network structure of amorphous PUs; glass transition and phase transformations in linear and cross-linked PUs; the  interrelationship between kinetics of PU formation and their bulk properties. The effective stiffness of PU chains was claimed to depend on the intrinsic flexibility of oligomer blocks, on their overall content and on the number of urethane groups per chain repeating unit. Studies of the effect of chemical composition on structure and thermodynamic properties of linear PUs based on low molar mass glycols, and of cross-linked PUs containing oligoglycol blocks had shown the possibility to obtain a variety of random copolyurethanes using different glycols or diisocyanates. The degree of crystallinity, polymorphism, glass transition interval, etc. could be varied over broad limits by changing the nature and/or relative content of PU chain components.

Joint research with Yu. Yu. Kercha and L.M. Sergeeva had also revealed that the properties of bulk PUs were determined by those of soft oligomeric blocks; the effective network of PUs comprised both chemical cross-links interchain physical bonds.

As demonstrated in one of the first studies of the network structure in PUs, the physical network made the major contribution to the effective density of such networks; the resulting high mobility of the latter was the natural explanation for the rapid equilibration of a new structural state arrived at after application of the external mechanical force. Subsequent research efforts were focused on synthesis and physical chemical characterization of interpenetrating polymer networks (IPNs) based on PUs.

The book entitled Adsorption of Polymers published by Yu.S. Lipatov and L.M. Sergeeva in 1972 (Naukova Dumka, Kyiv) and immediately translated in the USA (John Wiley & Sons), was the first treatise of polymer adsorption worldwide; the topics included not only a comprehensive summary of the current state-of-the-art, but also a formulation of new concepts of polymer adsorption from concentrated solutions (theory of the aggregative adsorption) and of the structure of adsorption layers.

Much attention was also paid to publication of reference books and handbooks: the Handbook of Polymer Chemistry published by Yu.S. Lipatov (in collaboration with A.E. Nesterov, T.M. Gritsenko and R.A. Veselovsky) in 1971 (Naukova Dumka, Kyiv) was the first such edition in the USSR.

In December of 1969, Yu.S. Lipatov was elected the corresponding Member and in December of 1973, he became the full Member of the Academy of Sciences of Ukraine. Beginning mid-1970’s, Yu.S. Lipatov started the physicochemical research in two new areas, those of polymer blends and of IPNs. These trends, together with the one on physical chemistry of interfacial phenomena in polymer

composite materials, are still being actively explored. During the same period, Yu.S. Lipatov became interested in general problems of the colloid chemistry of polymers and gave (1975) the definition of its object.

In 1977, i. e. 10 years since his first book issuing, Yu.S. Lipatov published the fundamental treatise under the same title, Physical Chemistry of Filled Polymers (Khimia, Moscow); its English translation was soon published in Great Britain (British Library, RAPRA, 1979). The book contained both the update variant of the experimental data available, as well as the presentation of general physicochemical concepts of polymer reinforcement which explicitly accounted for the decisive contribution of boundary layers at the polymer – filler interface to physical and mechanical properties of bulk polymer composites. In recognition of fundamental contributions to the field of the physical chemistry of composite polymer materials, in 1980 the Academy of Sciences of Ukraine awarded Yu.S. Lipatov with the L.V. Pisarzhevsky Prize in Physical Chemistry.

In 1979, Yu.S. Lipatov (in collaboration with L.M. Sergeeva) published the first book on IPNs worldwide entitled Interpenetrating Polymer Networks (Naukova Dumka, Kyiv). In this book the impact of incompatibility of components on the thermodynamic state and relaxation behavior of IPNs was explicitly accounted for. An analysis of the structure and thermodynamic properties of IPNs gave evidence for their two phase, heterogeneous state; hence, the then-dominating

concept of the topological interpenetrating of two component networks proved invalid (as was the concept of an ideal network structure in general). Filled IPNs were introduced as a new class of heterogeneous polymer composite materials.

During the period of 1965-1982, Yu.S. Lipatov organized and chaired five All-Union Conferences on chemistry and physical chemistry of PUs, and five Symposia on interfacial phenomena in polymers. The results of research in the latter field were summarized by Yu. S. Lipatov in the book entitled Interphase Phenomena in Polymers (Naukova Dumka, Kyiv, 1980).

Development of new fabrication technologies of films and adhesives on PU base which were first tested on the small scale at the IMC pilot plant, and thereafter were implemented on the large scale in the industry of Ukraine, had won to Yu.S. Lipatov and his team the State Prize of the Republic of Ukraine in the Field of Science and Technology (1981).

During 1970-1980’s, Yu.S. Lipatov made many efforts for introduction of many technologies developed both in his department and in other departments of the IMC in different industrial centers (Zaporozhye, Tula, Syzran, Lyubertsy, etc.).

   He and Prof. R.A. Veselovsky spent many days in Siberia inspecting the course of implementation of materials produced at the IMC pilot plant in the construction of the famous Baikal-Amur railroad.

In 1981, the Presidium of the Academy of Sciences of Ukraine had officially acknowledged the progress of the IMC in the field of polymer composite materials in the memorandum by which this field was registered as the leading one in the IMC. A further evidence for the indisputable leading position of the IMC in this field within the USSR was the publication by Yu.S. Lipatov in 1984 of two books entitled.

Thermodynamics of Polymer Solutions and Blends (in collaboration with A.E. Nesterov) and Colloid Chemistry of Polymers. The latter book was dedicated to the memory of Yu.S. Lipatov’s father, S.M. Lipatov, who passed away in 1961;

the English translation of this book was published in Netherlands (Elsevier, 1988) and received positive reviews in the leading international journals. In 1984, Yu. S. Lipatov also published the popular science book entitled Future of Polymer Composites (Naukova Dumka, Kyiv).

Beginning from 1986, Yu.S. Lipatov and some of his staffers became active in two research fields: rheology and thermodynamics of polymer blends (together with E. V. Lebedev, A.E. Nesterov and V.F. Shumsky), and adsorption of polymer mixtures from dilute and semi-dilute solutions (together with T.T. Todosiychuk and V.N. Chornaya). The first team (in collaboration with Prof. V.N. Kuleznev,Moscow Institute of Chemical Technology) had discovered that some physicochemical properties of liquid polymer blends pass through extreme (e. g., minimum of shear viscosity and maximum of thermodynamic potential) during their transition from the single-phase state into two-phase, heterogeneous state. This hitherto unheard-of behavior of such systems in the course of their microphase separation was recognized as a discovery (National Patent Service of the USSR, diploma Ne 374 dated from January 20, 1992). The second team proved experimentally the crucial importance of the critical concentration for coils overlap and of the thermodynamic compatibility of component polymers on salient features of adsorption of their mixtures from solution.

In mid-1980’s, the attention of Yu.S. Lipatov was attracted to general problems of the assessment of the value of scientific research. His team developed a new nomenclature of research subjects for academic institutions, and recommended the criteria of objective, multi-factor evaluation of the value of a basic research theme, other than the familiar science citation index. Within the methodology of this scheme, the following problems could be solved: optimum realization of a scientific potential; increase of research efficiency; economic feasibility of practical introduction of basic research data into industry, etc.

In 1986, the research activity of Yu.S. Lipatov and his coworkers was summarized in the two-volume edition, Filled Polymers (vol. 1) and Polymer Blends and Alloys (vol. 2), under the common title Physical Chemistry of Multicomponent Polymer Systems (Naukova Dumka, Kyiv). During the same

period, he wrote and/or edited several Handbooks, such as Phase State of Polymer Solutions and Blends (by Yu.S. Lipatov and A.E. Nesterov, Naukova Dumka, Kyiv, 1987), and Handbook on Physical Chemistry of Polymers (Naukova Dumka, Kyiv) in three volumes: Properties of Polymer Solutions and Blends (vol. 1, by A.E. Nesterov, 1984); Properties of Bulk Polymers  vol. 2, by V.P. Privalko, 1984); IR and NMR Spectroscopy of Polymers (by G.M. Semenovich and T.S. Khramova, 1985). Beginning from the 1970’s, Yu.S. Lipatov chaired the Section Polymer Composite Materials of the Program of Multilateral! Scientific Cooperation between Academies of Sciences of Socialist Countries. Over the years of his scientific career, Yu.S. Lipatov scored an impressive record of lectures and presentations at many National and International Conferences: see the list below.

Invited lectures: Rubber and Plastics Association of Great Britain (1965); Gordon Conferences (USA, 1975); American Chemical Society (USA, 1991); IUPAC Symposia and Microsymposia (Germany, 1967,1973, 1992, 1993; Hungary, 1968; Canada, 1969; Netherlands, 1970, 1990; Czechoslovakia, 1972, 1974, 1976, 1989; France, 1973; Great Britain, 1973; Bulgaria, 1982; Greece, 1988; Japan, 1990, 1998; USA, 1991; Sweden, 1994, 1996; Iran, 1994; Poland, 1998; Czech Republic, 2005) International Rubber Conferences (Kyiv, 1978; Moscow, 1984; Prague, 1989);

Visiting professorship: Case Western Reserve University (USA, 1990); Chalmers University of Technology (Sweden, 1996); Universities of London, York, Sheffield, Manchester, Glasgow (Great Britain, 1999); Institute of Chemistry of University of Miskolc (Hungary, 1999) Iowa State University of Science and Technology (USA, 2000).

Over many years, Yu.S. Lipatov was the member of the Scientific Council on Polymers, Academy of Sciences of the USSR; member of the Editorial Board of the journal Polymer Sciences (1976-1988); chairman of the Scientific Council, Section of Chemistry and Chemical Technology, Academy of Sciences of Ukraine; member of the Editorial Boards of the Ukrainian Chemical Journal and the Reports of the Academy of Sciences of Ukraine. Beginning from 1965, he served as the Editor-in-Chief of the local journal Synthesis and Physical Chemistry of Polymers (transformed on his initiative into Compositional Polymer Materials in 1978). During several years since mid-1970’s, Yu.S. Lipatov was the member of the Expert Council on Organic Chemistry of the Supreme Council of Scientific Certification of the USSR.

Much attention was paid by Yu.S. Lipatov to pedagogical activities. He was a supervisor of 50 PhD theses, and a scientific consultant of DSc theses of 10 staffers of his department (Yu. Yu. Kercha, L.M. Sergeeva, A.E. Nesterov, F.G. Fabulyak, VP. Privalko, E.V. Lebedev, V.V. Shilov, V.F. Shumsky, T.T. Alekseeva, T.T. Todosiychuk) and of a number of researchers from other Institutions. Over the years, he read lectures on different courses of polymer science in Tashkent (Polytechnic Institute), Erevan (State University), Vilnius (State University).

The new (and, apparently, one of the most productive) period of the scientific career of Yu.S. Lipatov started from the fall of 1985 when he !eft the official position of the Director of the IMC and switched over to pure scientific work. It was during this period that he formulated basically new ideas in several research subjects of his interest, such as:

— thermodynamic foundations of the concept of hybrid binders in polymer alloys;

— concept of self-organization during IPNs formation;

— concept of the non-equilibrium state of IPNs (i. e. the overall thermodynamic instability coexistent with the local quasiequilibrium) as a result of a non-equilibrium nature of their formation process.

The latter is explained by the process of microphase separation which sets on already at the early stage of transformation and which is caused by incipient thermodynamic incompatibility of two component networks during their simultaneous growth (together with A.E. Nesterov, V.V. Shilov, V.F. Rosovitsky and T.T. Alekseeva).

At the same time, the outcome of extensive studies of structure properties relationships in filled polymer alloys was the corresponding structural model (mid-1990’s) which explicitly took into consideration the gradients of composition and of the degree of phase separation of the matrix in the normal direction to the solid surface. This model should be equally applicable to both filled alloys of linear polymers and filled reactive alloys like IPNs. In the case of the former, the polymer — solid interface was shown (in collaboration with A.E. Nesterov) to have an effect on phase separation kinetics and structure of phases. In the case of the latter, the interrelationship between reaction kinetics and processes of microphase separation through the universal parameter, degree of segregation, was experimentally established and verified (together with T.T. Alekseeva, V.F. Rosovitsky), as were also basic physical-chemical principles of polymer alloys (1990) and thermodynamic features of gradient IPNs (together with L.V. Karabanova, 1992-1994).

Since 1995, new concepts of non-equilibrium surface segregation at the polymer alloy/solid interface and of adhesion of polymer alloys to solids have been developed. In the domain of interfacial phenomena, the basically important rule of

interfacial equilibrium (together with A.E. Fainerman) was formulated, and the dependence of the experimentally measured critical surface tension on that of the wetting liquid was established. A new class of surface active agents (flexible chain

oligomers with lyophilic end-groups) with 1-10 orders of magnitude higher surface activity compared to conventional surfactants, named as “bi-anchor surfactants”, was proposed (in collaboration with V. V. Shevchenko, A.E. Fainerman). New

concepts of adhesion in filled polymers and polymer blends were developed (together with V.F. Babich and T.T. Todosiychuk).

In 1985 Yu.S. Lipatov organized, and chaired up to 1995 the annual Kyiv Macromolecular Symposia “By the Golden Gate”; each symposium had on its agenda the current problem of polymer science, which was discussed by a limited number of invited scientists from Ukraine, Russia and other countries.

During that period, the following new books by Yu.S. Lipatov were published:

— Physicochemical Principles of Polymer Filling (Khimia, Moscow, 1991) — the update of the latest progress in the field of polymer composites;

— Polymer Reinforcement (ChemTech Pubi., Toronto, 1994) — a summary of past research and an overview of new problems of reinforcement of linear polymer blends, of surface segregation, of filler effect on IPNs, etc.;

— Thermodynamics of Polymer Blends (in collaboration with A.E. Nesterov; Technomic Publ. Co, Lancaster — Basel, 1997) — the first ever monograph on that subject in which the effect of polymer — solid interface on the thermodynamics of phase equilibria in polymer blends was explicitly accounted for.

During 1995-2006 the research in the field of adsorption of polymer mixtures and surface segregation in polymer systems received intensive development (T.T. Todosiychuk and V.N. Chornaya). For the first time the peculiarities of such adsorption connected with the thermodynamic incompatibility of

components in a solution and the distinction of the adsorbate's affinity to the adsorbent surface have been established.

The influence of a ratio of the adsorbate surface to the volume of a solution from which adsorption is proceeded on isotherms of adsorption and on the characteristic of adsorption layers has been investigated in detail. These results are generalized in

two articles in the Encyclopedia of Colloid and Interface Science (2002). The research in the field of phase-separated Interpenetrating polymer networks have received new development (T.T. Alekseeva, N.V. Babkina, N.V. Yarovaya).

The mechanism of formation of an interface layer between coexisting phases is established and the parameters determining its fraction are determined. The dependence of the layer fraction on the introduction of filler in the reaction system is shown. For the first time, research has been carried out in the field of compatibility of phase-separated IPNs. The correlation of the nature and quantity of compatibilizer with viscoelastic properties of system and the fraction of interface layer is established. In some works done together with L.F. Kosyanchuk the reaction formation of blends of linear polymers, its kinetics, phase separation and influence of filler were investigated. These researches have allowed developing new ideas about physical properties and a phase state of the filled blends of linear polymers and about behavior of blends and IPNs on the interface with a solid.

Since 2000 together with G.V. Kozlov there was given the fractal analysis of the properties of nanocomposites and disperse-filled polymers and of interphase layers. The peculiarities of reinforcement of composites by nanoparticles have been shown and the fractal treatment of adhesion was offered. In 2001 Yu.S. Lipatov published the book Phase-Separated Interpenetrating Polymer Networks (Dnipropetrovsk, USChTU), which summarized and generalized the currently available data and author’s data about the properties, structure, kinetics of formation and thermodynamics of IPNs.

In total, during his professional career, Yu.S. Lipatov had published 19 monographs and over 1300 papers in national and international journals; the practical value of his basic research may be assessed from more than 140 national patents

(“Author’s Certificates”) granted him and his coworkers.

In 1990, Yu.S. Lipatov was awarded the title of the Honoured Person in Science and Technology of Ukraine and was elected a member of the Academy of Creative Endeavor of the USSR (currently: The International Academy of Creative Endeavor, Moscow — San Diego). In 1997, Yu.S. Lipatov was awarded the Paul J. Flory prize of the International Academy of Creative Endeavor for fundamental contributions to polymer science.

In 1998 Yu.S. Lipatov was awarded the Third Class Order “For merits” That year the Academy of Sciences of Ukraine awarded Yu.S. Lipatov with the A.I. Kiprianov Prize for the series of the scientific works The Alloys of the Linear and Cross-Linked Polymers and Their Reinforcement. 

In 2005, Yu.S. Lipatov left the management of the Department of Physical Chemistry of Polymers created by him in 1965 and passed to the position of the management adviser of the Institute of Macromolecular Chemistry of the National Academy of Sciences of Ukraine. 

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