Wyniki wyszukiwania - Biblioteka Nauki

1

Synteza amfifilowych kopolimerów szczepionych metodą kontrolowanej (ko)polimeryzacji rodnikowej hydrofilowego makromonomeru poli(tlenku etylenu)

100%

Neugebauer D.

|

tom [Z] 62, 1-2

49-66

EN

A combination of hydrophilic and hydrophobic characters in one macromolecule of a polymer provides amphiphilic behavior [1, 2]. Such unique properties, which have found significant interest, are exhibited by graft copolymers containing poly(ethylene oxide) (PEO) as side chains attached to the backbone (Scheme 1) [20]. They have greatly expanded a class of materials important for science and biomedicine. This review article describes the PEO graft copolymers prepared by a variety of synthetic procedures used for the atom transfer radical (co)polymerization (ATRP) (Scheme 2) [15-17], i.e. directly by the grafting through, which is also named as the macromonomer method or by the grafting from technique, which requires the use of a multifunctional macroinitiator. Densely homografted copolymers also called molecular brushes [21-25] were obtained by homopolymerization of PEO macromonomer (Scheme 3). The density of PEO grafts was decreased in the copolymerization of PEO macromonomer with a low molecular weight comonomer resulting in loosely grafted copolymers contai-ning uniform PEO side chains (Scheme 4) [46-48]. Consequently, the copolymerization of two macromonomers yielded heterografted brushes (Scheme 5) [21, 23, 26, 45, 53-57]. In this case, the composition of copolymers was designed by the selection of proper comonomers with comparable (rM1 = rM2/rM1 ~ rM2) or different (rM1 > rM2, rM1 < rM2) reactivity ratios, which can form alternating/ random copolymers or spontaneous gradient of PEO chains along backbone, respectively. Using monofunctional macroinitiators with comb or linear composition for polymerization of PEO macromonomer resulted in comb-comb [31] or semi-comb diblock copolymers [21, 23, 27-30]. The reverse structures were also obtained, when the PEO graft copolymers were applied as the monofunctional macroinitiators [31, 32]. The use of polymeric multifunctional macroinitiators (graft or linear) in the polymerization of monomer or macromonomer led to the heterografted copolymers (Scheme 4) [32, 50, 51] or more complexed double grafted copolymers (Scheme 3) [25]. The applications of the PEO graft copolymers in numerous fields are also presented to show their versatile potential [25, 26, 46, 53, 55, 56, 68-76].

2

O metodach syntezy polieterów z monometrów oksiranowych

63%

Stolarzewicz A. , Neugebauer D.

|

tom [Z] 54, 1-2

127-138

EN

Methods of the oxiranes polymerization and the influence of the process conditions on the structure and properties of polyethers obtained are discussed. There are presented new methods for the synthesis of polyethers with hydroxyl end groups. In one of them double metal cyanide (DMC) complexes are used for the polymerization of propylene oxide and other oxiranes. The high activity is shown by a system containing Zn3(Co(CN) 6) 2 with the addition of zinc chloride, dimethoxyethane and water. Diols and triols with Mn up to 10 000, and with a very low amount of the monol fraction are obtained from propylene oxide. Potassium hydride and a crown ether are applied as the anionic initiator system in another method. Polymers of propylene oxide are formed in this case with Mn within the range between 6 000 and 12 000. They are mainly diols and they also contain the monol fraction. The chain transfer reaction to the monomer does not occur or its rate is strongly limited in the polymerization of some other oxiranes by potassium hydride. It allows to obtain the molecular weight of polyethers higher than that in the presence of the anionic initiators known so far. The Mn = 39 000 is found for example for poly(butylene oxide).

3

Polimeryzacja oksiranów w obecności wodorku potasu

51%

Stolarzewicz A. , Neugebauer D. , Grobelny J. , Grobelny Z.

|

tom T. 43, nr 7-8

443-449

PL

Stwierdzono, że w obecności układu wodorek potasu/eter koronowy anionowa polimeryzacja oksiranów przebiega w temperaturze pokojowej. Otrzymano polimery eteru butylowoglicydylowego o stosunku Mw/ Mn < 1,1. Makrocząsteczki poli(eteru butylowoglicydylowego) są (po hydrolizie) obustronnie zakończone grupą hydroksylową; nie obserwuje się tu reakcji przeniesienia łańcucha na monomer. Natomiast poli-meryzacji tlenku_propylenu (TP) towarzyszą reakcje uboczne, a stosunek Mw/ Mn powstającego polimeru wynosi ok. 1,8. Za-proponowano mechanizm polimeryzacji TP w obecności wo-dorku potasu, wyjaśniający powstawanie na jej początkowym etapie dipotasowego glikolanu propylenowego jako głównego produktu. Rodzaj użytego eteru koronowego -18--crown-6 i dicykloheksano-18-crown-6- nie wpływa na szybkość polimeryzacji TP, natomiast drugi z tych eterów powoduje powstawanie polimerów o niemal dwukrotnie większym ciężarze cząsteczkowym.

EN

The potassium hydride/18-crown-6 system was found to pro-mote anionic polymerization of oxiranes at room temperature to yield, e.g., poly(butoxymethyl oxirane)s with My,/Mn< 1.1 and with each macromolecule hydroxy-terminated (after hydrolysis) on both ends. No chain transfer reaction on the monomer was found to occur. Methyloxirane (or propylene oxide, PO) was found to polymerize with side reactions occurring; M;(,/M,, was 1.8. A polymerization mechanism was suggested to explain the formation of di-potassium propylene glycol as the major product at the initial stage. In the presence of dicyclohexane-18-crcwn-6, the rate of polymerization of PO was the same. However, the molecular weight of the resulting polymer was twice as high.