Emile Franta

Macromonomers: Synthesis, characterization and applications

The first part of this review critically examines the various attempts to prepare macromonomers: Anionic and cationic polymerization for synthesizing living polymers have been preferred whenever possible but two-step radical polymerizations making use of efficient transfer agents have also been applied.

Grafting and branching of polymers

This review summarizes the present state of investigations concerning synthesis of various types of model macromolecules. Emphasis was given to those methods which enable preparation of well characterized macromolecules, suited well enough for morphological and thermodynamic investigations in dilute solution, and to get information on the influence of heterocontact interactions and/or of enhanced segment density on the properties of the polymers considered. It can be seen that for such an aim, the anionic polymerization techniques which are versatile and well adapted to such problems, have yielded decisive progress. The main disadvantage of these methods is that the number of adequate monomers is rather limited. Other polymerization techniques do not involve active sites which retain their activity long enough to be of great interest for such synthesis.

Synthesis of polyethylene oxide macromers

SummaryAnionic “living” polymerization of oxirane was shown to be efficient for the synthesis of polyethylene oxide macromers. The double bond at chainend was introduced either upon initiation or upon deactivation. The macromers obtained were characterized carefully to establish quantitatively the presence of the end-standing double bond. The species are well defined and of narrow molecular weight distribution.

An efficient bifunctional lithium-organic initiator to be used in apolar solvents

Abstract Upon reaction of m -diisopropenylbenzene (DIB) with two mole equivalents of s-butyllithium (BuLi) in benzene solution a diadduct is formed predominantly. It was identified by proton n.m.r. and by mass spectrometry. Some oligomers are formed, next to the diadduct, at the expense of the monoadduct. When the addition reaction is carried out to completion, precipitation eventually occurs. If this solution is used as it is formed, before precipitation has occurred, to initiate the polymerization of styrene or of dienes in non-polar solvents, the polymers formed exhibit the molecular weights expected, narrow molecular weight distributions and two lithium-organic sites per polymer chain. This bifunctional lithium-organic initiator is efficient, in the absence of any polar additive, and should find suitable applications for the synthesis of triblock copolymers, of model networks and of telechelic polymers.

Kinetics of addition of butyllithium onto diisopropenylbenzene

Abstract The kinetics of the addition reaction between butyllithium and diisopropenylbenzene (DIB) were investigated in non-polar solvents. It has been established that the two double bonds of meta-DIB are almost isoreactive, as expected; for the para-isomer however the first addition is faster than the second. The overall rate of reaction is also greater for para-DIB. This kinetic study is of great use, since the diadduct behaves as an efficient bifunctional anionic initiator which can be used in non-polar solvents.

Synthesis of polytetrahydrofurane macromers by cationic deactivation

We are presenting here results obtained with the alternaCe method: The polymerization of oxolane (THF) is initiated; once the chains have reached the average length that is desired, an efficient unsaturated nucleophile is added, whereupon deactivation occurs, and terminal double bonds are introduced. A method similar to ours has been published recently by Asami et al. (3). A detailed characterization was performed on the samples obtained to establish whether the samples exhibit the structure expected.

Synthesis and Applications of Macromonomers

The methods of synthesis of macromonomers are reviewed with emphasis on those based on anionic polymerization, and capable of yielding samples of well defined molecular weights and low polydispersity. Homopolymerization of macromonomers - either free radical or anionic - yields highly branched and compact macromolecules, The chief interest of macromonomers is to provide an easy access to graft copolymers upon free radical copolymerization with an acrylic or vinylic comonomer.

Kinetics of anionic polymerization of styrene in tetrahydrofurane

Abstract Electric conductivity measurements and determinations of the kinetics of the anionic polymerization of styrene in tetrahydrofurane at −70° with potassium as a counter-ion have been carried out. The electrolytic dissociation constant was found to be 8·5 × 10−7 moles l−1, and the propagation constants for contact ion pairs and free ions were found to be 3 and 2400 l. mole−1 sec−1, respectively. These results are discussed and compared with those of the sodium salt of living polystyrene.

Cationic telomerization of isobutylene

SummaryCationic telomerization has been attempted by reacting BF3 onto isobutylene in the presence of acetic anhydride: Under proper experimental conditions, we obtained only one product — a cetoester monoadduct CH3COCH2-C(CH3)2-O-COCH3 -. In order to study the initiation step, we have reacted a preformed salt CH3CO+SbF6− onto isobutylene in the presence of acetic anhydride and shown that the acetylium salt is efficient and that termination by esterification is surprisingly high.