Polycaprolactone (PCL) is an important polymer due to its mechanical properties, miscibility with a large range of other polymers and biodegradability. Two main pathways to produce polycaprolactone have been described in the literature: the polycondensation of a hydroxycarboxylic acid: 6-hydroxyhexanoic acid, and the ring-opening polymerisation (ROP) of a lactone: e-caprolactone (e-CL). This critical review summarises the different conditions which have been described to synthesise PCL, and gives a broad overview of the different catalytic systems that were used (enzymatic, organic and metal catalyst systems). A surprising variety of catalytic systems have been studied, touching on virtually every section of the periodic table. A detailed list of reaction conditions and catalysts/initiators is given and reaction mechanisms are presented where known. Emphasis is put on the ROP pathway due to its prevalence in the literature and the superior polymer that is obtained. In addition, ineffective systems that have been tried to catalyse the production of PCL are included in the electronic supplementary information for completeness (141 references).

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Synthesis of polycaprolactone: a review

Conflict and Conflict Management.

Polymeric materials, natural and unnatural, are indispensable to the modern society. They are widely used from everyday life usages as commodity materials to industry and technology usages in the fields such as electronics, machinery, communications, transportations, pharmacy, and medicine as highly advanced materials. Today, it is hard to think of the present society without polymeric materials. Developments of various polymeric materials have been owed to epoch-making innovative works as exemplified typically by the discovery of Ziegler-Natta catalyst,1-3 the concept of living polymerization,4 the discovery of conducting polymers,5 and the discovery of metathesis catalyst.6,7 These observations demonstrate that new polymeric materials are often brought about by new production methods including polymerization catalysts. Historically, polymerization catalysts utilized classical catalysts of acids (Brønsted acids, Lewis acids, and various cations), bases (Lewis bases and various anions), and radical generating compounds since the 1920s, the early stage of polymer chemistry. In the following * To whom correspondence should be addressed. Fax/Tel: (+81)-75-7247688. E-mail: kobayash@kit.ac.jp. † Kyoto Institute of Technology and Emeritus Professor of Kyoto University. ‡ Kyoto University. Chem. Rev. 2009, 109, 5288–5353 5288

Enzymatic polymer synthesis: an opportunity for green polymer chemistry.

Recent advances in the synthesis of aliphatic polyesters by ring-opening polymerization.

The present article comprehensively reviews the macromolecular synthesis using enzymes as catalysts. Among the six main classes of enzymes, the three classes, oxidoreductases, transferases, and hydrolases, have been employed as catalysts for the in vitro macromolecular synthesis and modification reactions. Appropriate design of reaction including monomer and enzyme catalyst produces macromolecules with precisely controlled structure, similarly as in vivo enzymatic reactions. The reaction controls the product structure with respect to substrate selectivity, chemo-selectivity, regio-selectivity, stereoselectivity, and choro-selectivity. Oxidoreductases catalyze various oxidation polymerizations of aromatic compounds as well as vinyl polymerizations. Transferases are effective catalysts for producing polysaccharide having a variety of structure and polyesters. Hydrolases catalyzing the bond-cleaving of macromolecules in vivo, catalyze the reverse reaction for bond forming in vitro to give various polysacchar...

Enzymes as Green Catalysts for Precision Macromolecular Synthesis

We report the ring-opening polymerization reaction of e-caprolactone in supercritical carbon dioxide (scCO2) using an enzyme catalyst, Lipase B from Candida antarctica supported on macroporous beads (Novozym-435). Ring-opening polymerization of lactones is more commonly performed in organic solvents or in bulk using a Lewis acid catalyst. Recently there has been much interest in the replacement of such catalysts by enzymes. We demonstrate that the enzymatic route is viable in scCO2, yielding poly(e-caprolactone) (Mn = 12 000−37 000 g mol-1) with molecular weights very similar to those obtained from the same enzyme catalysts in organic solvents, but with lower polydispersities (typical PDI = 1.4−1.6) and higher yields of polymer product (typically 95−98%). In the same process the unique “gaslike” mass transfer properties of scCO2 can also be exploited to remove quantitatively any unconverted monomer and low molecular weight oligomers by scCO2 extraction. It is also shown that the enzyme catalyst can be cle...

Enzyme-Catalyzed Ring-Opening Polymerization of ε-Caprolactone in Supercritical Carbon Dioxide

Regulatory Focus and Opportunism in the Alliance Development Process

We propose a framework to understand interpartner harmony in strategic alliances. Interpartner harmony in strategic alliances denotes the mutual understanding that alliance members accomplish by managing commitment and forbearance in the context of their interdependence. We proceed from the notion that the pervasive conflict-based view of alliances has clouded the consideration of the quest for harmony as a significant factor in alliance dynamics. We believe that alliances have an inbuilt resilience that makes the emergence of harmony a natural outcome, through the joint exercise of commitment and forbearance, even as conflict and opportunism persist as inevitable challenges. We describe the four kinds of interpartner harmony in alliances – superficial, specious, constrained and communal – based on the degrees of commitment and forbearance. We also discuss the salience of each of these interpartner harmony types in the three principal types of alliances (equity joint ventures, minority equity alliances and nonequity alliances). Implications of the analysis are discussed for further research as well as managerial practice.

Interpartner harmony in strategic alliances: managing commitment and forbearance

International alliance negotiations are now a pervasive feature of the contemporary global economy. As the alliancing firms cross national boundaries to forge cooperative partnerships they face the inevitable necessity of bridging the cultural divide to ensure successful negotiation. Existing research has focused primarily on the impact of national cultural differences in shaping negotiating strategies and ensuing outcomes. Less attention has been paid to how negotiators from different cultures understand and manage the ambiguity of international alliance negotiations. We employ the theoretical lens of sensemaking to understand how negotiators embedded in different cultures manage simultaneously the task and cultural related ambiguity that they are confronted with. This perspective suggests the critical role that ‘tertius iungens’ (the ‘third who joins’) plays in facilitating the negotiation process. The ‘tertius iungens’ represents a form of intermediation that acts as a catalyst in the negotiation process. We propose three alternative types of intermediation, namely, cognitive, affective, and holistic and provide illustrative examples of these types of intermediation. We conclude by highlighting the theoretical and managerial significance of our framework and by suggesting future directions for research.

Culture and International Alliance Negotiations: A Sensemaking Perspective

Purpose – The purpose of this paper is to propose a framework for understanding how alliance partners interpret alliance functioning and how these interpretations shape their subsequent behaviors. Also, to discuss how interpretive schemes in cross‐national strategic alliances impact upon the management of the problems arising from the cultural conflicts and discrepancies inherent in such alliances.Design/methodology/approach – Proceeding from the notion that interpretive schemes have important implications for the evolution of cross‐national alliances, the paper describes the two fundamental interpretive schemes that relate to sensemaking – that of sensemaking of and in chaos, and examines how an appreciation of these interpretive schemes enable us to better manage cultural conflicts and discrepancies that inevitably arise in cross‐national alliances.Findings – The framework makes clear that the two types of interpretive schemes − “sensemaking of chaos” and “sensemaking in chaos” − need to be appreciated ...

Rajesh Kumar

Papers

Enzyme-Catalyzed Ring-Opening Polymerization of ε-Caprolactone in Supercritical Carbon Dioxide

Regulatory Focus and Opportunism in the Alliance Development Process

Interpartner harmony in strategic alliances: managing commitment and forbearance

Culture and International Alliance Negotiations: A Sensemaking Perspective

Interpretive schemes in cross‐national alliances: Managing conflicts and discrepancies