Introduction of a New Coupling Agent for Selective Coupling of Hydroxy and Amino Group‐Containing Polymers

Abstract

IntroductionMulticomponent mixtures of polycondensates are widely spread in polymer chemistry. In order to achieve good adhesion and compatibility, covalent links between the components are desirable. It is evident that such linkages may be formed by the same reactions that usually occur during the synthesis of polycondensates. These are reactions of the terminal groups among each other but also transreactions between the terminal groups and the linking groups of polycondensates, such as, for example, transesterification and transamidation. In blends of condensates, such reactions result in in-situ formation of block copolymers in the interface between the components.In order to achieve high degrees of conversion, severe conditions such as good vacuum, high reaction temperatures, and long reaction times are demanded. In addition, suitable catalysts and effective mixing have to be applied. Under such conditions, undesired side reactions and by-products may complicate process control and limit the final product properties. This especially applies to the preparation of defined multi-block copolymers. Transreactions that occur during the entire process make it practically impossible to control the length of the Feature ArticleA new bifunctional coupling agent with an oxazinone and a lactamate group is synthesized. It is shown by means of model reactions that in the presence of aliphatic hydroxy compounds the reaction of the coupling agent is highly selective. At 220 8C, a conversion of the lactamate group of about 90% is observed under elimination of lactam. In a second reaction the oxazinone group is converted with an aliphatic amino compound. This high selectivity is utilized in the synthesis of segmented polyester/polyamide block copolymers by sequential conversion of the coupling agent with hydroxyterminated polyesters [poly(butylene terephthalate) (PBT) and polycaprolactone (PCL)] and aminoterminated polyamide 12 (PA12) under the conditions of reactive extrusion. In the case of the PA12/PBT block copolymer, ductile behavior is observed, whereas the PA12/PCL block copolymer shows elastic properties. Both polymers are phase separated on the nanometer-scale, as evidenced by AFM and SEM. The thermal behavior of the polymers is affected by the influence of the individual blocks.

Alternating block copolymers based on polyamide‐12 and polycaprolactone

“…Under the conditions chosen, the reactions were complete at the latest after 10 min which is very fast compared to conventional polycondensation reactions. The formation of block copolymers 3 can unambiguously be confirmed from 1 H NMR spectroscopic measurements 16. The aromatic region of the spectra shows only signals of the linking group between the blocks.…”

“…A series of block copolymers was prepared using a procedure similar to that described earlier 16. As shown in Scheme , the reaction was performed in two steps.…”

“…Otherwise, 1 H NMR spectroscopic measurements confirmed complete conversion of terminal groups and coupling agent 1 in the extracted products. More information is given elsewhere 16. Five block copolymers of varying block length were prepared by combination of the two PA12 and the three PCL oligomers: PCL/PA12[10/2], PCL/PA12[10/5], PCL/PA12[3/2], PCL/PA12[2/2] and PCL/PA12[2/5].…”

“…To overcome this problem, we developed coupling agents with two different reactive groups which address different terminal groups selectively 11–16. As an example we showed that it is possible to synthesize segmented polyester/amide block copolymers by a sequential conversion of hydroxy‐terminated PCL and amino‐terminated PA12 with a new coupling agent ( 1 in Scheme ) possessing oxazinone and lactamate groups 16. The reaction as shown in Scheme ensures that coupling only proceeds between polyamide and polyester oligomers.…”

Synthesis and Structural NMR Characterization of Novel PPG/PCL Conetworks Based upon Heterocomplementary Coupling Reactions

“…This severely restricts the formation of defined structures. To overcome this problem, we utilized coupling agents with different highly selective reacting groups which enabled us to perform heterocomplementary carboxy/amino and hydroxy/amino group coupling. By this way, defined block and graft copolymers based on polyamides, polyesters and polyethers were synthesized in the melt …”